In this work,we design and fabricate AlGaN/GaN-based Schottky barrier diodes(SBDs)on a silicon substrate with a trenched n^(+)-GaN cap layer.With the developed physical models,we find that the n^(+)-GaN cap layer prov...In this work,we design and fabricate AlGaN/GaN-based Schottky barrier diodes(SBDs)on a silicon substrate with a trenched n^(+)-GaN cap layer.With the developed physical models,we find that the n^(+)-GaN cap layer provides more electrons into the AlGaN/GaN channel,which is further confirmed experimentally.When compared with the reference device,this increases the two-dimensional electron gas(2DEG)density by two times and leads to a reduced specific ON-resistance(Ron,sp)of~2.4 mΩ·cm^(2).We also adopt the trenched n^(+)-GaN structure such that partial of the n^(+)-GaN is removed by using dry etching process to eliminate the surface electrical conduction when the device is set in the off-state.To suppress the surface defects that are caused by the dry etching process,we also deposit Si_(3)N_(4)layer prior to the deposition of field plate(FP),and we obtain a reduced leakage current of~8×10^(−5)A·cm^(−2)and breakdown voltage(BV)of 876 V.The Baliga’s figure of merit(BFOM)for the proposed structure is increased to~319 MW·cm^(−2).Our investigations also find that the pre-deposited Si_(3)N_(4)layer helps suppress the electron capture and transport processes,which enables the reduced dynamic R_(on,sp).展开更多
Owing to the low p-type doping efficiency in the hole injection layers(HILs)of GaN-based ultra-violet(UV)vertical-cavity surface-emitting laser(VCSEL),effective hole injection in multi-quantum wells(MQW)is not achieve...Owing to the low p-type doping efficiency in the hole injection layers(HILs)of GaN-based ultra-violet(UV)vertical-cavity surface-emitting laser(VCSEL),effective hole injection in multi-quantum wells(MQW)is not achieved,significantly limiting the photoelectric performance of UV VCSELs.We developed a slope-shaped HIL and an EBL structure in AlGaN-based UV VCSELs.In this study,by improving hole in-jection efficiency,the hole concentration in the HIL is increased,and the hole barrier at the electron barrier layer(EBL)/HIL interface is decreased.This minimises the hindering effect of hole injection.A mathematic-al model of this structure was established using a commercial software,photonic integrated circuit simulator in three-dimension(PICS3D).We conducted simulations and theoretical analyses of the band structure and carrier concentration.Introducing polarisation doping through the Al composition gradient in the HIL en-hanced the hole concentration,thereby improving the hole injection efficiency.Furthermore,modifying the EBL eliminated the abrupt potential barrier for holes at the HIL/EBL interface,smoothing the valence band.This improved the stimulated radiative recombination rate in the MQW,increasing the laser power.There-fore,the sloped p-type layer can enhance the optoelectronic performance of UV VCSELs.展开更多
This study begins with the fabrication and simulation of high-performance back-illuminated AlGaN-based solar-blind ultraviolet(UV)photodetectors.Based on the photodetectors,a low-noise,high-gain UV detection system ci...This study begins with the fabrication and simulation of high-performance back-illuminated AlGaN-based solar-blind ultraviolet(UV)photodetectors.Based on the photodetectors,a low-noise,high-gain UV detection system circuit is designed and fabricated,enabling the detection,acquisition,and calibration of weak solar-blind UV signals.Experimental results demonstrate that under zero bias conditions,with a UV light power density of 3.45μW/cm^(2) at 260 nm,the sample achieves a peak responsivity(R)of 0.085 A·W^(−1),an external quantum efficiency(EQE)of 40.7%,and a detectivity(D^(*))of 7.46×10^(12) cm·Hz^(1/2)·W^(−1).The system exhibits a bandpass characteristic within the 240–280 nm wavelength range,coupled with a high signal-to-noise ratio(SNR)of 39.74 dB.展开更多
240 nm AlGaN-based micro-LEDs with different sizes are designed and fabricated.Then,the external quantum efficiency(EQE)and light extraction efficiency(LEE)are systematically investigated by comparing size and edge ef...240 nm AlGaN-based micro-LEDs with different sizes are designed and fabricated.Then,the external quantum efficiency(EQE)and light extraction efficiency(LEE)are systematically investigated by comparing size and edge effects.Here,it is revealed that the peak optical output power increases by 81.83%with the size shrinking from 50.0 to 25.0μm.Thereinto,the LEE increases by 26.21%and the LEE enhancement mainly comes from the sidewall light extraction.Most notably,transversemagnetic(TM)mode light intensifies faster as the size shrinks due to the tilted mesa side-wall and Al reflector design.However,when it turns to 12.5μm sized micro-LEDs,the output power is lower than 25.0μm sized ones.The underlying mechanism is that even though protected by SiO2 passivation,the edge effect which leads to current leakage and Shockley-Read-Hall(SRH)recombination deteriorates rapidly with the size further shrinking.Moreover,the ratio of the p-contact area to mesa area is much lower,which deteriorates the p-type current spreading at the mesa edge.These findings show a role of thumb for the design of high efficiency micro-LEDs with wavelength below 250 nm,which will pave the way for wide applications of deep ultraviolet(DUV)micro-LEDs.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
In recent years,the development of wafer-level GaN nanowires photocatalyst loaded onto silicon substrates has progressed rapidly depending on its simplicity of instrumentation,collection and separation from the water....In recent years,the development of wafer-level GaN nanowires photocatalyst loaded onto silicon substrates has progressed rapidly depending on its simplicity of instrumentation,collection and separation from the water.Accordingly,the wafer-level GaN-based nanowires(GaN NWs)photocatalyst can be a fabulous candidate for the application in the field of photocatalytic hydrogen evolution reaction(PHER)and provides a novel route to address the environmental and energy crisis.Herein,a range of innovative strategies to improve the performance of GaN NWs photocatalyst are systematically summarized.Then,the solar-to-hydrogen conversion efficiency,the characteristics of GaN NWs system,the cost of the origin material required,as well as the stability,activity and the corrosion resistance to seawater are discussed in detail as some of the essential conditions for advancing its large-scale industry-friendly application.Last but not least,we provide the potential application of this system for splitting seawater to produce hydrogen and point out the direction for overcoming the barriers to future industrial-scale implementation.展开更多
To improve the optical and electrical properties of AlGaN-based deep ultraviolet lasers,an inverse-trapezoidal electron blocking layer is designed.Lasers with three different structural electron blocking layers of rec...To improve the optical and electrical properties of AlGaN-based deep ultraviolet lasers,an inverse-trapezoidal electron blocking layer is designed.Lasers with three different structural electron blocking layers of rectangular,trapezoidal and inverse-trapezoidal structures are established.The energy band,electron concentration,electron current density,P-I and V-I characteristics,and the photoelectric conversion efficiency of different structural devices are investigated by simulation.The results show that the optical and electrical properties of the inversetrapezoidal electron blocking layer laser are better than those of rectangular and trapezoidal structures,owing to the effectively suppressed electron leakage.展开更多
The upper waveguide （UWG） has direct influences on the optical and electrical characteristics of the violet laser diode （LD） by changing the optical field distribution or barrier of the electron blocking layer （...The upper waveguide （UWG） has direct influences on the optical and electrical characteristics of the violet laser diode （LD） by changing the optical field distribution or barrier of the electron blocking layer （EBL）. In this study, a series of InGaN-based violet LDs with different UWGs are investigated systematically with LASTIP software. It is found that the output light power （OLP） under an injecting current of 120 mA or the threshold current （Ith） is deteriorated when the UWG is u-In0.02Ga0.98N/GaN or u-In0.02Ga0.98N/AlxGa1-xN （0 ≤ x ≤ 0.1）, which should be attributed to small optical confinement factor （OCF） or severe electron leakage. Therefore, a new violet LD structure with u-In0.02Ga0.98N/GaN/Al0.05Ga0.95N multiple layer UWG is proposed to reduce the optical loss and increase the barrier of EBL. Finally, the output light power under an injecting current of 120 mA is improved to 176.4 mW.展开更多
The low internal quantum efficiency(IQE)of AlGaN-based deep ultraviolet light emitting diode(DUV-LED)limits its wider application.The main reasons for low IQE include low carrier concentration,poor carrier location an...The low internal quantum efficiency(IQE)of AlGaN-based deep ultraviolet light emitting diode(DUV-LED)limits its wider application.The main reasons for low IQE include low carrier concentration,poor carrier location and large defects.The bending of energy band between AlGaN electron blocking layer and conduction layer obstructs transport of holes to multiple quantum wells.In this paper,we propose a gradual Al-composition p-type AlGaN(p-AlGaN)conduction layer to improve the light emitting properties of AlGaN-based DUV-LED.Increased carrier concentration in the active region enhances the effective radiative recombination rate of the LED.Consequently,the IQE of our optimazited DUV-LED is increased by 162%in comparison with conventional DUV-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
AlGaN-based back-illuminated solar-blind ultraviolet(UV)p–i–n photodetectors(PDs)with high quantum efficiency are fabricated on sapphire substrates.To improve the overall performance of the PD,a series of structural...AlGaN-based back-illuminated solar-blind ultraviolet(UV)p–i–n photodetectors(PDs)with high quantum efficiency are fabricated on sapphire substrates.To improve the overall performance of the PD,a series of structural design considerations and growth procedures are implemented in the epitaxy process.A distinct wavelength-selective photo-response peak of the PD is obtained in the solar-blind region.When operating in photovoltaic mode,the PD exhibits a solar-blind/UV rejection ratio of up to 4 orders of magnitude and a peak responsivity of~113.5 mA/W at 270 nm,which corresponds to an external quantum efficiency of~52%.Under a reverse bias of-5 V,the PD shows a low dark current of~1.8 pA and an enhanced peak quantum efficiency of~64%.The thermal noise limited detectivity is estimated to be~3.3×10^(13) cm·Hz^(1/2)W^(-1).展开更多
Al_(0.5)Ga_(0.5)N-based metal-semiconductor-metal photodetectors(PDs)with a large device area of 5×5 mm^(2) are fabricated on a sapphire substrate,which are tested for vacuum ultraviolet light detection by using ...Al_(0.5)Ga_(0.5)N-based metal-semiconductor-metal photodetectors(PDs)with a large device area of 5×5 mm^(2) are fabricated on a sapphire substrate,which are tested for vacuum ultraviolet light detection by using a synchrotron radiation source.The PD exhibits low dark current of less than 1 pA under 30 V bias and a spectral cutoff around 260 nm,corresponding to the energy bandgap of Al_(0.5)Ga_(0.5)N.A peak photo-responsivity of 14.68 mA/W at 250 nm with a rejection ratio(250/360 nm)of more than four orders of magnitude is obtained under 30 V bias.For wavelength less than 170 nm,the photoresponsivity of the PD is found to increase as wavelength decreases,which is likely caused by the enhanced photoemission effect.展开更多
The kink effect in current-voltage （IV） characteristic s seriously deteriorates the performance of a GaN-based HEMT. Based on a series of direct current （DC） IV measurements in a GaN-based HEMT with an AlGaN back ...The kink effect in current-voltage （IV） characteristic s seriously deteriorates the performance of a GaN-based HEMT. Based on a series of direct current （DC） IV measurements in a GaN-based HEMT with an AlGaN back barrier, a possible mechanism with electron-trapping and detrapping processes is proposed. Kink-related deep levels are activated by a high drain source voltage （Vds） and located in a GaN channel layer. Both electron trapping and detrapping processes are accomplished with the help of hot electrons from the channel by impact ionization. Moreover, the mechanism is verified by two other DC IV measurements and a model with an expression of the kink current.展开更多
基金supported by National Natural Science Foundation of China under grant U23A20361Key Area R&D Program of Guangdong Province under grant 2022B0701180001.
文摘In this work,we design and fabricate AlGaN/GaN-based Schottky barrier diodes(SBDs)on a silicon substrate with a trenched n^(+)-GaN cap layer.With the developed physical models,we find that the n^(+)-GaN cap layer provides more electrons into the AlGaN/GaN channel,which is further confirmed experimentally.When compared with the reference device,this increases the two-dimensional electron gas(2DEG)density by two times and leads to a reduced specific ON-resistance(Ron,sp)of~2.4 mΩ·cm^(2).We also adopt the trenched n^(+)-GaN structure such that partial of the n^(+)-GaN is removed by using dry etching process to eliminate the surface electrical conduction when the device is set in the off-state.To suppress the surface defects that are caused by the dry etching process,we also deposit Si_(3)N_(4)layer prior to the deposition of field plate(FP),and we obtain a reduced leakage current of~8×10^(−5)A·cm^(−2)and breakdown voltage(BV)of 876 V.The Baliga’s figure of merit(BFOM)for the proposed structure is increased to~319 MW·cm^(−2).Our investigations also find that the pre-deposited Si_(3)N_(4)layer helps suppress the electron capture and transport processes,which enables the reduced dynamic R_(on,sp).
文摘Owing to the low p-type doping efficiency in the hole injection layers(HILs)of GaN-based ultra-violet(UV)vertical-cavity surface-emitting laser(VCSEL),effective hole injection in multi-quantum wells(MQW)is not achieved,significantly limiting the photoelectric performance of UV VCSELs.We developed a slope-shaped HIL and an EBL structure in AlGaN-based UV VCSELs.In this study,by improving hole in-jection efficiency,the hole concentration in the HIL is increased,and the hole barrier at the electron barrier layer(EBL)/HIL interface is decreased.This minimises the hindering effect of hole injection.A mathematic-al model of this structure was established using a commercial software,photonic integrated circuit simulator in three-dimension(PICS3D).We conducted simulations and theoretical analyses of the band structure and carrier concentration.Introducing polarisation doping through the Al composition gradient in the HIL en-hanced the hole concentration,thereby improving the hole injection efficiency.Furthermore,modifying the EBL eliminated the abrupt potential barrier for holes at the HIL/EBL interface,smoothing the valence band.This improved the stimulated radiative recombination rate in the MQW,increasing the laser power.There-fore,the sloped p-type layer can enhance the optoelectronic performance of UV VCSELs.
基金supported by the Director’s Fund for the‘Climbing Plan’of the National Space Science Centre of the Chinese Academy of Sciences(No.E2PD10011S)the National Engineering Research Centre for Mobile Private Networks Project(No.BJTU20221102).
文摘This study begins with the fabrication and simulation of high-performance back-illuminated AlGaN-based solar-blind ultraviolet(UV)photodetectors.Based on the photodetectors,a low-noise,high-gain UV detection system circuit is designed and fabricated,enabling the detection,acquisition,and calibration of weak solar-blind UV signals.Experimental results demonstrate that under zero bias conditions,with a UV light power density of 3.45μW/cm^(2) at 260 nm,the sample achieves a peak responsivity(R)of 0.085 A·W^(−1),an external quantum efficiency(EQE)of 40.7%,and a detectivity(D^(*))of 7.46×10^(12) cm·Hz^(1/2)·W^(−1).The system exhibits a bandpass characteristic within the 240–280 nm wavelength range,coupled with a high signal-to-noise ratio(SNR)of 39.74 dB.
基金This work was supported by National Key R&D Program of China(2022YFB3605103)the National Natural Science Foundation of China(62204241,U22A2084,62121005,and 61827813)+3 种基金the Natural Science Foundation of Jilin Province(20230101345JC,20230101360JC,and 20230101107JC)the Youth Innovation Promotion Association of CAS(2023223)the Young Elite Scientist Sponsorship Program By CAST(YESS20200182)the CAS Talents Program(E30122E4M0).
文摘240 nm AlGaN-based micro-LEDs with different sizes are designed and fabricated.Then,the external quantum efficiency(EQE)and light extraction efficiency(LEE)are systematically investigated by comparing size and edge effects.Here,it is revealed that the peak optical output power increases by 81.83%with the size shrinking from 50.0 to 25.0μm.Thereinto,the LEE increases by 26.21%and the LEE enhancement mainly comes from the sidewall light extraction.Most notably,transversemagnetic(TM)mode light intensifies faster as the size shrinks due to the tilted mesa side-wall and Al reflector design.However,when it turns to 12.5μm sized micro-LEDs,the output power is lower than 25.0μm sized ones.The underlying mechanism is that even though protected by SiO2 passivation,the edge effect which leads to current leakage and Shockley-Read-Hall(SRH)recombination deteriorates rapidly with the size further shrinking.Moreover,the ratio of the p-contact area to mesa area is much lower,which deteriorates the p-type current spreading at the mesa edge.These findings show a role of thumb for the design of high efficiency micro-LEDs with wavelength below 250 nm,which will pave the way for wide applications of deep ultraviolet(DUV)micro-LEDs.
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 Natural Science Foundation of China(No.51902101,22479079)Innovation Support Programme(Soft Science Research)Project Achievements of Jiangsu Province(BK20231514)+3 种基金the Youth Natural Science Foundation of Hunan Province(No.2021JJ40044)Natural Science Foundation of Jiangsu Province(No.BK20201381)Science Foundation of Nanjing University of Posts and Telecommunications(Nos.NY219144,NY221046)the National College Student Innovation and Entrepre-neurship Training Program(No.202210293083Y).
文摘In recent years,the development of wafer-level GaN nanowires photocatalyst loaded onto silicon substrates has progressed rapidly depending on its simplicity of instrumentation,collection and separation from the water.Accordingly,the wafer-level GaN-based nanowires(GaN NWs)photocatalyst can be a fabulous candidate for the application in the field of photocatalytic hydrogen evolution reaction(PHER)and provides a novel route to address the environmental and energy crisis.Herein,a range of innovative strategies to improve the performance of GaN NWs photocatalyst are systematically summarized.Then,the solar-to-hydrogen conversion efficiency,the characteristics of GaN NWs system,the cost of the origin material required,as well as the stability,activity and the corrosion resistance to seawater are discussed in detail as some of the essential conditions for advancing its large-scale industry-friendly application.Last but not least,we provide the potential application of this system for splitting seawater to produce hydrogen and point out the direction for overcoming the barriers to future industrial-scale implementation.
基金the National Natural Science Foundation of China under Grant No.61176008the Special Project for Intergovernment Collaboration of State Key Research and Development Program under Grant No.2016YFE0118400+1 种基金the Key Project of Science and Technology of Henan Province under Grant No.172102410062the National Natural Science Foundation of China-Henan Provincial Joint Fund for Key Project under Grant No.U1604263.
文摘To improve the optical and electrical properties of AlGaN-based deep ultraviolet lasers,an inverse-trapezoidal electron blocking layer is designed.Lasers with three different structural electron blocking layers of rectangular,trapezoidal and inverse-trapezoidal structures are established.The energy band,electron concentration,electron current density,P-I and V-I characteristics,and the photoelectric conversion efficiency of different structural devices are investigated by simulation.The results show that the optical and electrical properties of the inversetrapezoidal electron blocking layer laser are better than those of rectangular and trapezoidal structures,owing to the effectively suppressed electron leakage.
基金Project supported by the National Key R&D Program of China(Grant Nos.2016YFB0400803 and 2016YFB0401801)the National Natural Science Foundation of China(Grant Nos.61674138,61674139,61604145,61574135,61574134,61474142,61474110,61377020,and 61376089)+1 种基金the Science Challenge Project,China(Grant No.TZ2016003)the Beijing Municipal Science and Technology Project,China(Grant No.Z161100002116037)
文摘The upper waveguide （UWG） has direct influences on the optical and electrical characteristics of the violet laser diode （LD） by changing the optical field distribution or barrier of the electron blocking layer （EBL）. In this study, a series of InGaN-based violet LDs with different UWGs are investigated systematically with LASTIP software. It is found that the output light power （OLP） under an injecting current of 120 mA or the threshold current （Ith） is deteriorated when the UWG is u-In0.02Ga0.98N/GaN or u-In0.02Ga0.98N/AlxGa1-xN （0 ≤ x ≤ 0.1）, which should be attributed to small optical confinement factor （OCF） or severe electron leakage. Therefore, a new violet LD structure with u-In0.02Ga0.98N/GaN/Al0.05Ga0.95N multiple layer UWG is proposed to reduce the optical loss and increase the barrier of EBL. Finally, the output light power under an injecting current of 120 mA is improved to 176.4 mW.
基金supported by the Key Research and Development Program of Shandong Province(Nos.2018GGX101027,2017GGX201002 and 2016GGX4101)the Union Funds of Guizhou Science and Technology Department and Guizhou Minzu University China(No.LH20157221)+1 种基金the Yantai“13th Five-Year”Marine Economic Innovation and Development Demonstration City Project(No.YHCXZB-L-201703)Fundamental Research Funds of Shandong University in China(Nos.2018WLJH87,2018JCG01 and 2017TB0021)。
文摘The low internal quantum efficiency(IQE)of AlGaN-based deep ultraviolet light emitting diode(DUV-LED)limits its wider application.The main reasons for low IQE include low carrier concentration,poor carrier location and large defects.The bending of energy band between AlGaN electron blocking layer and conduction layer obstructs transport of holes to multiple quantum wells.In this paper,we propose a gradual Al-composition p-type AlGaN(p-AlGaN)conduction layer to improve the light emitting properties of AlGaN-based DUV-LED.Increased carrier concentration in the active region enhances the effective radiative recombination rate of the LED.Consequently,the IQE of our optimazited DUV-LED is increased by 162%in comparison with conventional DUV-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Supported by the State Key Program for Basic Research of China under Grant Nos 2010CB327504,2011CB922100 and 2011CB301900the National Natural Science Foundation of China under Grant Nos 60825401,60936004,11104130 and 60990311.
文摘AlGaN-based back-illuminated solar-blind ultraviolet(UV)p–i–n photodetectors(PDs)with high quantum efficiency are fabricated on sapphire substrates.To improve the overall performance of the PD,a series of structural design considerations and growth procedures are implemented in the epitaxy process.A distinct wavelength-selective photo-response peak of the PD is obtained in the solar-blind region.When operating in photovoltaic mode,the PD exhibits a solar-blind/UV rejection ratio of up to 4 orders of magnitude and a peak responsivity of~113.5 mA/W at 270 nm,which corresponds to an external quantum efficiency of~52%.Under a reverse bias of-5 V,the PD shows a low dark current of~1.8 pA and an enhanced peak quantum efficiency of~64%.The thermal noise limited detectivity is estimated to be~3.3×10^(13) cm·Hz^(1/2)W^(-1).
基金Supported by the National Basic Research Program of China under Grant Nos 2010CB327504,2011CB922100 and 2011CB301900the National Natural Science Foundation of China under Grant Nos 60936004 and 11104130+1 种基金the Natural Science Foundation of Jiangsu Province under Grant Nos BK2011556 and BK2011050the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Al_(0.5)Ga_(0.5)N-based metal-semiconductor-metal photodetectors(PDs)with a large device area of 5×5 mm^(2) are fabricated on a sapphire substrate,which are tested for vacuum ultraviolet light detection by using a synchrotron radiation source.The PD exhibits low dark current of less than 1 pA under 30 V bias and a spectral cutoff around 260 nm,corresponding to the energy bandgap of Al_(0.5)Ga_(0.5)N.A peak photo-responsivity of 14.68 mA/W at 250 nm with a rejection ratio(250/360 nm)of more than four orders of magnitude is obtained under 30 V bias.For wavelength less than 170 nm,the photoresponsivity of the PD is found to increase as wavelength decreases,which is likely caused by the enhanced photoemission effect.
基金Project supported by the Program for New Century Excellent Talents in University,China (Grant No.NCET-12-0915)
文摘The kink effect in current-voltage （IV） characteristic s seriously deteriorates the performance of a GaN-based HEMT. Based on a series of direct current （DC） IV measurements in a GaN-based HEMT with an AlGaN back barrier, a possible mechanism with electron-trapping and detrapping processes is proposed. Kink-related deep levels are activated by a high drain source voltage （Vds） and located in a GaN channel layer. Both electron trapping and detrapping processes are accomplished with the help of hot electrons from the channel by impact ionization. Moreover, the mechanism is verified by two other DC IV measurements and a model with an expression of the kink current.
