Although the 5G wireless network has made significant advances,it is not enough to accommodate the rapidly rising requirement for broader bandwidth in post-5G and 6G eras.As a result,emerging technologies in higher fr...Although the 5G wireless network has made significant advances,it is not enough to accommodate the rapidly rising requirement for broader bandwidth in post-5G and 6G eras.As a result,emerging technologies in higher frequencies including visible light communication(VLC),are becoming a hot topic.In particular,LED-based VLC is foreseen as a key enabler for achieving data rates at the Tb/s level in indoor scenarios using multi-color LED arrays with wavelength division multiplexing(WDM)technology.This paper proposes an optimized multi-color LED array chip for high-speed VLC systems.Its long-wavelength GaN-based LED units are remarkably enhanced by V-pit structure in their efficiency,especially in the“yellow gap”region,and it achieves significant improvement in data rate compared with earlier research.This work investigates the V-pit structure and tries to provide insight by introducing a new equivalent circuit model,which provides an explanation of the simulation and experiment results.In the final test using a laboratory communication system,the data rates of eight channels from short to long wavelength are 3.91 Gb/s,3.77 Gb/s,3.67 Gb/s,4.40 Gb/s,3.78 Gb/s,3.18 Gb/s,4.31 Gb/s,and 4.35 Gb/s(31.38 Gb/s in total),with advanced digital signal processing(DSP)techniques including digital equalization technique and bit-power loading discrete multitone(DMT)modulation format.展开更多
A thin GaN LED film, grown on 2-inch-diameter sapphire substrates, is separated by laser lift-off. Atom force microscopy （AFM） and the double-crystal X-ray diffraction （XRD） have been employed to characterize the ...A thin GaN LED film, grown on 2-inch-diameter sapphire substrates, is separated by laser lift-off. Atom force microscopy （AFM） and the double-crystal X-ray diffraction （XRD） have been employed to characterize the performance of Gan before and after the lift-off process. It is demonstrated that the separation and transfer processes do not alter the crystal quality of the GaN films obviously. InGaN/GaN multi-quantum-wells （MQW＇s） structure is grown on the separated sapphire substrate later and is compared with that grown on the conventional substmte under the same condition by using PL and XRD spectrum.展开更多
Progress with GaN-based light emitting diodes （LEDs） that incorporate nanostructures is reviewed, especially the re- cent achievements in our research group. Nano-patterned sapphire substrates have been used to grow...Progress with GaN-based light emitting diodes （LEDs） that incorporate nanostructures is reviewed, especially the re- cent achievements in our research group. Nano-patterned sapphire substrates have been used to grow an A1N template layer for deep-ultraviolet （DUV） LEDs. One efficient surface nano-texturing technology, hemisphere-cones-hybrid nanostruc- tures, was employed to enhance the extraction efficiency of InGaN flip-chip LEDs. Hexagonal nanopyramid GaN-based LEDs have been fabricated and show electrically driven color modification and phosphor-free white light emission because of the linearly increased quantum well width and indium incorporation from the shell to the core. Based on the nanostruc- tures, we have also fabricated surface plasmon-enhanced nanoporous GaN-based green LEDs using AAO membrane as a mask. Benefitting from the strong lateral SP coupling as well as good electrical protection by a passivation layer, the EL intensity of an SP-enhanced nanoporous LED was significantly enhanced by 380%. Furthermore, nanostructures have been used for the growth of GaN LEDs on amorphous substrates, the fabrication of stretchable LEDs, and for increasing the 3-dB modulation bandwidth for visible light communication.展开更多
We use a simple and controllable method to fabricate GaN-based light-emitting diodes （LEDs） with 22° undercut sidewalls by the successful implementation of the inductively coupled plasma reactive ion etching （...We use a simple and controllable method to fabricate GaN-based light-emitting diodes （LEDs） with 22° undercut sidewalls by the successful implementation of the inductively coupled plasma reactive ion etching （ICP-RIE）. Our exper- iment results show that the output powers of the LEDs with 22° undercut sidewalls are 34.8 rnW under a 20-mA current injection, 6.75% higher than 32.6 mW, the output powers of the conventional LEDs under the same current injection.展开更多
Rapid improvement in the efficiency of GaN-based LEDs not only speed up its applications for general illumination, but offer the possibilities for data transmission. This review is to provide an overview of current pr...Rapid improvement in the efficiency of GaN-based LEDs not only speed up its applications for general illumination, but offer the possibilities for data transmission. This review is to provide an overview of current progresses of GaN-based LEDs for light communications. The modulation bandwidth of GaN-based LEDs has been first improved by optimizing the LED epilayer structures and the modulation bandwidth of 73 MHz was achieved at the driving current density of 40 A/cm2 by changing the multi-quantum well structures. After that, in order to increase the current density tolerance, different parallel flip-chip micro-LED arrays were fabricated. With a high injected current density of ~7900 A/cm2, a maximum modulation bandwidth of ~227 MHz was obtained with optical power greater than 30 mW. Besides the increase of carrier concentrations, the radiative recombination coefficient B was also enhanced by modifying the photon surrounding environment based on some novel nanostructures such as resonant cavity, surface plasmon, and photonic crystals. The optical 3 dB modulation bandwidth of GaN-based nanostructure LEDs with Ag nanoparticles was enhanced by 2 times compared with GaN-based nanostructure LEDs without Ag nanoparticles.Our results demonstrate that using the QW-SP coupling can effectively help to enhance the carrier spontaneous emission rate and also increase the modulation bandwidth for LEDs, especially for LEDs with high intrinsic IQE. In addition, we discuss the progress of the faster color conversion stimulated by GaN-based LEDs.展开更多
A correlation model between micro plasma noise and gamma irradiation of GaN-based LED is built.The reverse bias I-V characteristics and micro-plasma noise were measured in it, before and after Gamma irradiation. It is...A correlation model between micro plasma noise and gamma irradiation of GaN-based LED is built.The reverse bias I-V characteristics and micro-plasma noise were measured in it, before and after Gamma irradiation. It is found that even after 30 krad Gamma irradiation, the GaN-based LED has soft breakdown failure. The reverse soft breakdown region current local instability of this device before irradiation is analyzed by the microplasma noise method. The results were obtained that if the GaN-based LED contained micro-plasma defects, it will fail after low doses（30 krad） of gamma irradiation. The results clearly reflect the micro-plasma defects induced carriers fluctuation noise and the local instability of GaN-based LED reverse bias current.展开更多
InGaN MQW LEDs, grown by metal-organic chemical vapor deposition (MOCVD) on Si(111) substrates, were successfully bonded and transferred onto new Si substrate. After chemical etching Si(111) substrate and inductively ...InGaN MQW LEDs, grown by metal-organic chemical vapor deposition (MOCVD) on Si(111) substrates, were successfully bonded and transferred onto new Si substrate. After chemical etching Si(111) substrate and inductively coupled plasma (ICP) etching the transferred LED film to Si-doped layer, a vertical structure GaN blue LEDs were then fabricated. The characteristics of the lateral structure LED (grown on Si) and the vertical structure LED (bonded on Si) were investigated. It shows the performance of ver- tical structure LEDs had obviously been improved compared to the lateral structure LEDs and the tensile stress in GaN layer of vertical structure LEDs is smaller than that in lateral structure LEDs.展开更多
A homemade 7×2 inch MOCVD system is presented.With this system,high quality GaN epitaxial layers,InGaN/GaN multi-quantum wells and blue LED structural epitaxial layers have been successfully grown. The non-unifor...A homemade 7×2 inch MOCVD system is presented.With this system,high quality GaN epitaxial layers,InGaN/GaN multi-quantum wells and blue LED structural epitaxial layers have been successfully grown. The non-uniformity of undoped GaN epitaxial layers is as low as 2.86%.Using the LED structural epitaxial layers, blue LED chips with area of 350×350μm2 were fabricated.Under 20 mA injection current,the optical output power of the blue LED is 8.62 mW.展开更多
GaN-based vertical light-emitting-diodes （V-LEDs） with an improved current injection pattern were fabricated and a novel current injection pattern of LEDs which consists of electrode-insulator-semiconductor （E1S） ...GaN-based vertical light-emitting-diodes （V-LEDs） with an improved current injection pattern were fabricated and a novel current injection pattern of LEDs which consists of electrode-insulator-semiconductor （E1S） structure was proposed. The EIS structure was achieved by an insulator layer （20-nm Ta2O5） deposited between the p-GaN and the ITO layer. This kind of EIS structure works through a defect-assisted tunneling mechanism to realize current injection and obtains a uniform current distribution on the chip surface, thus greatly improving the current spreading ability of LEDs. The appearance of this novel current injection pattern of V-LEDs will subvert the impression of the conventional LEDs structure, including simplifying the chip manufacture technology and reducing the chip cost. Under a current density of 2, 5, 10, and 25 A/cm2, the luminous uniformity was better than conventional structure LEDs. The standard deviation of power density distribution in light distribution was 0.028, which was much smaller than that of conventional structure LEDs and illustrated a huge advantage on the current spreading ability of EIS-LEDs.展开更多
The effect of AlGaN interlayer in quantum barrier on the electroluminescence characteristics of GaN-based green light emitting diodes(LEDs)grown on silicon substrate was investigated.The results show that AlGaN interl...The effect of AlGaN interlayer in quantum barrier on the electroluminescence characteristics of GaN-based green light emitting diodes(LEDs)grown on silicon substrate was investigated.The results show that AlGaN interlayer is beneficial to improve the luminous efficiency of LED devices and restrain the phase separation of In GaN.The former is ascribed to the inserted AlGaN layers can play a key role in determining the carrier distribution and screening dislocations in the active region,and the latter is attributed to the increased compressive stress in the quantum well.However,when the electrical stress aging tests were performed at a current density of 100 A/cm^2,LED devices with AlGaN interlayers are more likely to induce the generation/proliferation of defects in the active region under the effect of electrical stress,resulting in the reduced light output power at low current density.展开更多
GaN-based yellow light-emitting diodes(LEDs) on Si substrates are aged at a direct current density of 50 A/cm^2 for500 h. After the aging process, it can be found that the LEDs have a stable electrical property but th...GaN-based yellow light-emitting diodes(LEDs) on Si substrates are aged at a direct current density of 50 A/cm^2 for500 h. After the aging process, it can be found that the LEDs have a stable electrical property but their light output power is decayed by 4.01% at 35 A/cm^2. Additionally, the aging mechanism of GaN-based yellow LED is analyzed. It is found that the decay of light output power may be attributed to the following two reasons: one is the increase of Shockley–Rrad–Hall recombination and the other is the change of the transport path of holes via V-pits after aging, which may induce the radiative recombination current to decrease. In this paper, not only the aging mechanism of GaN-based yellow LED is investigated, but also a new possible research direction in LED aging is given.展开更多
Driven by the urgent demands for information technology,energy,and intelligent industry,third-generation semiconductor GaN has emerged as a pivotal component in electronic and optoelectronic devices.Fundamentally,piez...Driven by the urgent demands for information technology,energy,and intelligent industry,third-generation semiconductor GaN has emerged as a pivotal component in electronic and optoelectronic devices.Fundamentally,piezoelectric polarization is the most essential feature of GaN materials.Incorporating piezotronics and piezo-phototronics,GaN materials synergize mechanical signals with electrical and optical signals,thereby achieving multi-field coupling that enhances device performance.Piezotronics regulates the carrier transport process in micro-nano devices,which has been proven to significantly improve the performance of devices(such as high electron mobility transistors and microLEDs)and brings many novel applications.This review examines GaN material properties and the theoretical foundations of piezotronics and phototronics.Furthermore,it delves into the fabrication and integration processes of GaN devices to achieve state-of-the-art performance.Additionally,this review analyzes the impact of introducing three-dimensional stress and regulatory forces on the electrical and optical output performance of devices.Moreover,it discusses the burgeoning applications of GaN devices in neural sensing,optoelectronic output,and energy harvesting.The potential of piezotroniccontrolled GaN devices provides valuable insights for future research and the development of multi-functional,diversified electronic devices.展开更多
GaN-based irregular multiple quantum well （IMQW） structures assembled two different types of QWs emitting complementary wavelengths for dichromatic white light-emitting diodes （LEDs） are optimized in order to obta...GaN-based irregular multiple quantum well （IMQW） structures assembled two different types of QWs emitting complementary wavelengths for dichromatic white light-emitting diodes （LEDs） are optimized in order to obtain near white light emissions. The hole distributions and spontaneous emission spectra of the IMQW structures are analysed in detail by fully considering the effects of strain, well-coupling, valence band-mixing and polarization effect through employing a newly developed theoretical model from the k. p theory. Several structure parameters such as well material component, well width, layout of the wells and the thickness of harrier between different types of QWs are employed to analyse how these parameters together with the polarization effect influence the electronic and the optical properties of IMQW structure. Numerical results show that uniform hole distributions in different types of QWs are obtained when the number of the QWs emitting blue light is two, the number of the QWs emitting yellow light is one and the barrier between different types of QWs is 8nm in thickness. The near white light emission is realized using GaN-based IMQW structure with appropriate design parameters and injection level.展开更多
基金This research was funded by the National Key Research and Development Program of China(2022YFB2802803)the Natural Science Foundation of China Project(No.61925104,No.62031011,No.62201157,No.62074072).
文摘Although the 5G wireless network has made significant advances,it is not enough to accommodate the rapidly rising requirement for broader bandwidth in post-5G and 6G eras.As a result,emerging technologies in higher frequencies including visible light communication(VLC),are becoming a hot topic.In particular,LED-based VLC is foreseen as a key enabler for achieving data rates at the Tb/s level in indoor scenarios using multi-color LED arrays with wavelength division multiplexing(WDM)technology.This paper proposes an optimized multi-color LED array chip for high-speed VLC systems.Its long-wavelength GaN-based LED units are remarkably enhanced by V-pit structure in their efficiency,especially in the“yellow gap”region,and it achieves significant improvement in data rate compared with earlier research.This work investigates the V-pit structure and tries to provide insight by introducing a new equivalent circuit model,which provides an explanation of the simulation and experiment results.In the final test using a laboratory communication system,the data rates of eight channels from short to long wavelength are 3.91 Gb/s,3.77 Gb/s,3.67 Gb/s,4.40 Gb/s,3.78 Gb/s,3.18 Gb/s,4.31 Gb/s,and 4.35 Gb/s(31.38 Gb/s in total),with advanced digital signal processing(DSP)techniques including digital equalization technique and bit-power loading discrete multitone(DMT)modulation format.
基金the National Natural Science Foundation of China (No.60276029)the 863 Project ( 2004AA3 11020 and 2006AA032409)Natural Science Foundation of Fujian Province (2006H0092,A0210006,and 2005HZ1018).
文摘A thin GaN LED film, grown on 2-inch-diameter sapphire substrates, is separated by laser lift-off. Atom force microscopy （AFM） and the double-crystal X-ray diffraction （XRD） have been employed to characterize the performance of Gan before and after the lift-off process. It is demonstrated that the separation and transfer processes do not alter the crystal quality of the GaN films obviously. InGaN/GaN multi-quantum-wells （MQW＇s） structure is grown on the separated sapphire substrate later and is compared with that grown on the conventional substmte under the same condition by using PL and XRD spectrum.
基金Project supported by the National Natural Science Foundation of China(Grant No.61334009)the National High Technology Research and Development Program of China(Grant Nos.2015AA03A101 and 2014BAK02B08)+1 种基金China International Science and Technology Cooperation Program(Grant No.2014DFG62280)the"Import Outstanding Technical Talent Plan"and"Youth Innovation Promotion Association Program"of the Chinese Academy of Sciences
文摘Progress with GaN-based light emitting diodes （LEDs） that incorporate nanostructures is reviewed, especially the re- cent achievements in our research group. Nano-patterned sapphire substrates have been used to grow an A1N template layer for deep-ultraviolet （DUV） LEDs. One efficient surface nano-texturing technology, hemisphere-cones-hybrid nanostruc- tures, was employed to enhance the extraction efficiency of InGaN flip-chip LEDs. Hexagonal nanopyramid GaN-based LEDs have been fabricated and show electrically driven color modification and phosphor-free white light emission because of the linearly increased quantum well width and indium incorporation from the shell to the core. Based on the nanostruc- tures, we have also fabricated surface plasmon-enhanced nanoporous GaN-based green LEDs using AAO membrane as a mask. Benefitting from the strong lateral SP coupling as well as good electrical protection by a passivation layer, the EL intensity of an SP-enhanced nanoporous LED was significantly enhanced by 380%. Furthermore, nanostructures have been used for the growth of GaN LEDs on amorphous substrates, the fabrication of stretchable LEDs, and for increasing the 3-dB modulation bandwidth for visible light communication.
基金Project supported by the National High Technology Research and Development Program of China (Grant Nos.2011AA03A112,2011AA03A106,and 2013AA03A101)the National Natural Science Foundation of China (Grant Nos.11204360,61210014,and 61078046)+2 种基金the Science and Technology Innovation Program of Department of Education of Guangdong Province,China (Grant No.2012CXZD0017)the Industry–Academia Research Union Special Fund of Guangdong Province,China (Grant No.2012B091000169)the Science and Technology Innovation Platform of Industry–Academia Research Union of Guangdong Province–Ministry Cooperation Special Fund,China (Grant No.2012B090600038)
文摘We use a simple and controllable method to fabricate GaN-based light-emitting diodes （LEDs） with 22° undercut sidewalls by the successful implementation of the inductively coupled plasma reactive ion etching （ICP-RIE）. Our exper- iment results show that the output powers of the LEDs with 22° undercut sidewalls are 34.8 rnW under a 20-mA current injection, 6.75% higher than 32.6 mW, the output powers of the conventional LEDs under the same current injection.
基金supported by the National Natural Science Foundation of China(Grant No.11574306)the China International Science and Technology Cooperation Program(Grant No.2014DFG62280)the National High Technology Program of China(Grant No.2015AA03A101)
文摘Rapid improvement in the efficiency of GaN-based LEDs not only speed up its applications for general illumination, but offer the possibilities for data transmission. This review is to provide an overview of current progresses of GaN-based LEDs for light communications. The modulation bandwidth of GaN-based LEDs has been first improved by optimizing the LED epilayer structures and the modulation bandwidth of 73 MHz was achieved at the driving current density of 40 A/cm2 by changing the multi-quantum well structures. After that, in order to increase the current density tolerance, different parallel flip-chip micro-LED arrays were fabricated. With a high injected current density of ~7900 A/cm2, a maximum modulation bandwidth of ~227 MHz was obtained with optical power greater than 30 mW. Besides the increase of carrier concentrations, the radiative recombination coefficient B was also enhanced by modifying the photon surrounding environment based on some novel nanostructures such as resonant cavity, surface plasmon, and photonic crystals. The optical 3 dB modulation bandwidth of GaN-based nanostructure LEDs with Ag nanoparticles was enhanced by 2 times compared with GaN-based nanostructure LEDs without Ag nanoparticles.Our results demonstrate that using the QW-SP coupling can effectively help to enhance the carrier spontaneous emission rate and also increase the modulation bandwidth for LEDs, especially for LEDs with high intrinsic IQE. In addition, we discuss the progress of the faster color conversion stimulated by GaN-based LEDs.
基金Project supported by the Education Department Science and Technology Foundation of Jiangxi Province(No.GJJ160743)the Doctoral Research Start-Up Foundation of Jinggangshan University(No.JZB15001)
文摘A correlation model between micro plasma noise and gamma irradiation of GaN-based LED is built.The reverse bias I-V characteristics and micro-plasma noise were measured in it, before and after Gamma irradiation. It is found that even after 30 krad Gamma irradiation, the GaN-based LED has soft breakdown failure. The reverse soft breakdown region current local instability of this device before irradiation is analyzed by the microplasma noise method. The results were obtained that if the GaN-based LED contained micro-plasma defects, it will fail after low doses（30 krad） of gamma irradiation. The results clearly reflect the micro-plasma defects induced carriers fluctuation noise and the local instability of GaN-based LED reverse bias current.
基金supported by the 863 Project(Grant Nos.2005AA311010 and 2003AA302160)the Electronic Development Fund of Information Industry in China(Grant Nos.(2004)125 and(2004)479)Nanchang University Science Foundation.
文摘InGaN MQW LEDs, grown by metal-organic chemical vapor deposition (MOCVD) on Si(111) substrates, were successfully bonded and transferred onto new Si substrate. After chemical etching Si(111) substrate and inductively coupled plasma (ICP) etching the transferred LED film to Si-doped layer, a vertical structure GaN blue LEDs were then fabricated. The characteristics of the lateral structure LED (grown on Si) and the vertical structure LED (bonded on Si) were investigated. It shows the performance of ver- tical structure LEDs had obviously been improved compared to the lateral structure LEDs and the tensile stress in GaN layer of vertical structure LEDs is smaller than that in lateral structure LEDs.
基金Project supported by the National High Technology Research and Development Program of China(No.2006AA03A141)the Knowledge Innovation Engineering of the Chinese Academy of Sciences(No.YYYJ-0701-02)+2 种基金the National Natural Science Foundation of China (Nos.60890193,60906006)the State Key Development Program for Basic Research of China(Nos.2006CB604905,2010CB327503)the Knowledge Innovation Program of the Chinese Academy of Sciences(Nos.ISCAS2008T01,ISCAS2009L01,ISCAS2009L02)
文摘A homemade 7×2 inch MOCVD system is presented.With this system,high quality GaN epitaxial layers,InGaN/GaN multi-quantum wells and blue LED structural epitaxial layers have been successfully grown. The non-uniformity of undoped GaN epitaxial layers is as low as 2.86%.Using the LED structural epitaxial layers, blue LED chips with area of 350×350μm2 were fabricated.Under 20 mA injection current,the optical output power of the blue LED is 8.62 mW.
基金supported by the Natural Science Foundation of China(Nos.61306051,61306050)the National High Technology Program of China(No.2014AA032606)
文摘GaN-based vertical light-emitting-diodes （V-LEDs） with an improved current injection pattern were fabricated and a novel current injection pattern of LEDs which consists of electrode-insulator-semiconductor （E1S） structure was proposed. The EIS structure was achieved by an insulator layer （20-nm Ta2O5） deposited between the p-GaN and the ITO layer. This kind of EIS structure works through a defect-assisted tunneling mechanism to realize current injection and obtains a uniform current distribution on the chip surface, thus greatly improving the current spreading ability of LEDs. The appearance of this novel current injection pattern of V-LEDs will subvert the impression of the conventional LEDs structure, including simplifying the chip manufacture technology and reducing the chip cost. Under a current density of 2, 5, 10, and 25 A/cm2, the luminous uniformity was better than conventional structure LEDs. The standard deviation of power density distribution in light distribution was 0.028, which was much smaller than that of conventional structure LEDs and illustrated a huge advantage on the current spreading ability of EIS-LEDs.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2016YFB0400600 and 2016YFB0400601)the National Natural Science Foundation of China(Grant Nos.61704069 and 51705230)。
文摘The effect of AlGaN interlayer in quantum barrier on the electroluminescence characteristics of GaN-based green light emitting diodes(LEDs)grown on silicon substrate was investigated.The results show that AlGaN interlayer is beneficial to improve the luminous efficiency of LED devices and restrain the phase separation of In GaN.The former is ascribed to the inserted AlGaN layers can play a key role in determining the carrier distribution and screening dislocations in the active region,and the latter is attributed to the increased compressive stress in the quantum well.However,when the electrical stress aging tests were performed at a current density of 100 A/cm^2,LED devices with AlGaN interlayers are more likely to induce the generation/proliferation of defects in the active region under the effect of electrical stress,resulting in the reduced light output power at low current density.
基金Project supported by the National Natural Science Foundation for Young Scientists of China(Grant Nos.61704069 and 51602141)the National Key Research and Development Program of China(Grant No.2016YFB0400601)
文摘GaN-based yellow light-emitting diodes(LEDs) on Si substrates are aged at a direct current density of 50 A/cm^2 for500 h. After the aging process, it can be found that the LEDs have a stable electrical property but their light output power is decayed by 4.01% at 35 A/cm^2. Additionally, the aging mechanism of GaN-based yellow LED is analyzed. It is found that the decay of light output power may be attributed to the following two reasons: one is the increase of Shockley–Rrad–Hall recombination and the other is the change of the transport path of holes via V-pits after aging, which may induce the radiative recombination current to decrease. In this paper, not only the aging mechanism of GaN-based yellow LED is investigated, but also a new possible research direction in LED aging is given.
基金the support from the National Natural Science Foundation of China(Grant Nos.52173298,52192611 and 61904012)the National Key R&D Project from Minister of Science and Technology(2021YFA1201603)+1 种基金Beijing Natural Science Foundation(Z230024)the Fundamental Research Funds for the Central Universities。
文摘Driven by the urgent demands for information technology,energy,and intelligent industry,third-generation semiconductor GaN has emerged as a pivotal component in electronic and optoelectronic devices.Fundamentally,piezoelectric polarization is the most essential feature of GaN materials.Incorporating piezotronics and piezo-phototronics,GaN materials synergize mechanical signals with electrical and optical signals,thereby achieving multi-field coupling that enhances device performance.Piezotronics regulates the carrier transport process in micro-nano devices,which has been proven to significantly improve the performance of devices(such as high electron mobility transistors and microLEDs)and brings many novel applications.This review examines GaN material properties and the theoretical foundations of piezotronics and phototronics.Furthermore,it delves into the fabrication and integration processes of GaN devices to achieve state-of-the-art performance.Additionally,this review analyzes the impact of introducing three-dimensional stress and regulatory forces on the electrical and optical output performance of devices.Moreover,it discusses the burgeoning applications of GaN devices in neural sensing,optoelectronic output,and energy harvesting.The potential of piezotroniccontrolled GaN devices provides valuable insights for future research and the development of multi-functional,diversified electronic devices.
基金supported by the National Natural Science Foundation of China (Grant No. 60777013)the Nature Science Foundation of Beijing,China (Grant No. 4082023)the Excellent Doctoral Science and Technology Innovation Foundation of Beijing Jiaotong University,China (Grant No. 141063522)
文摘GaN-based irregular multiple quantum well （IMQW） structures assembled two different types of QWs emitting complementary wavelengths for dichromatic white light-emitting diodes （LEDs） are optimized in order to obtain near white light emissions. The hole distributions and spontaneous emission spectra of the IMQW structures are analysed in detail by fully considering the effects of strain, well-coupling, valence band-mixing and polarization effect through employing a newly developed theoretical model from the k. p theory. Several structure parameters such as well material component, well width, layout of the wells and the thickness of harrier between different types of QWs are employed to analyse how these parameters together with the polarization effect influence the electronic and the optical properties of IMQW structure. Numerical results show that uniform hole distributions in different types of QWs are obtained when the number of the QWs emitting blue light is two, the number of the QWs emitting yellow light is one and the barrier between different types of QWs is 8nm in thickness. The near white light emission is realized using GaN-based IMQW structure with appropriate design parameters and injection level.
