The InGaN films and GaN/InGaN/GaN tunnel junctions(TJs)were grown on GaN templates with plasma-assisted molecular beam epitaxy.As the In content increases,the quality of InGaN films grown on GaN templates decreases an...The InGaN films and GaN/InGaN/GaN tunnel junctions(TJs)were grown on GaN templates with plasma-assisted molecular beam epitaxy.As the In content increases,the quality of InGaN films grown on GaN templates decreases and the surface roughness of the samples increases.V-pits and trench defects were not found in the AFM images.p++-GaN/InGaN/n++-GaN TJs were investigated for various In content,InGaN thicknesses and doping concentration in the InGaN insert layer.The InGaN insert layer can promote good interband tunneling in GaN/InGaN/GaN TJ and significantly reduce operating voltage when doping is sufficiently high.The current density increases with increasing In content for the 3 nm InGaN insert layer,which is achieved by reducing the depletion zone width and the height of the potential barrier.At a forward current density of 500 A/cm^(2),the measured voltage was 4.31 V and the differential resistance was measured to be 3.75×10^(−3)Ω·cm^(2)for the device with a 3 nm p++-In_(0.35)Ga_(0.65)N insert layer.When the thickness of the In_(0.35)Ga_(0.65)N layer is closer to the“balanced”thickness,the TJ current density is higher.If the thickness is too high or too low,the width of the depletion zone will increase and the current density will decrease.The undoped InGaN layer has a better performance than n-type doping in the TJ.Polarization-engineered tunnel junctions can enhance the functionality and performance of electronic and optoelectronic devices.展开更多
Waveguide characteristics of symmetrical separate confinement heterojunction multi quantum well (SCH MQW) AlGaN/GaN/InGaN laser diode (LD) are studied by using one dimensional (1 D) transfer matrix waveguide appro...Waveguide characteristics of symmetrical separate confinement heterojunction multi quantum well (SCH MQW) AlGaN/GaN/InGaN laser diode (LD) are studied by using one dimensional (1 D) transfer matrix waveguide approach.Aiming at photon confinement factor,threshold current,and power efficiency,layers design for SCH MQW LD is optimized.The optimal layers parameters are 3 periods In 0.02 Ga 0.98 N/In 0.15 Ga 0.85 N QW for active layer,In 0.1 Ga 0 9 N for waveguide layer with 90nm thick,and 120×(2 5nm/2 5nm) Al 0.25 Ga 0 75 N/GaN supper lattices for cladding layer with the laser wavelength of 396 6nm.展开更多
The influences of stress on the properties of InGaN/GaN multiple quantum wells （MQWs） grown on silicon substrate were investigated. The different stresses were induced by growing InGaN and A1GaN insertion layers （I...The influences of stress on the properties of InGaN/GaN multiple quantum wells （MQWs） grown on silicon substrate were investigated. The different stresses were induced by growing InGaN and A1GaN insertion layers （IL） respectively before the growth of MQWs in metal-organic chemical vapor deposition （MOCVD） system. High resolution x-ray diffrac- tion （HRXRD） and photoluminescence （PL） measurements demonstrated that the InGaN IL introduced an additional ten- sile stress in n-GaN, which released the strain in MQWs. It is helpful to increase the indium incorporation in MQWs. In comparison with MQWs without the IL, the wavelength shows a red-shift. A1GaN IL introduced a compressive stress to compensate the tensile stress, which reduces the indium composition in MQWs. PL measurement shows a blue-shift of wavelength. The two kinds of ILs were adopted to InGaN/GaN MQWs LED structures. The same wavelength shifts were also observed in the electroluminescence （EL） measurements of the LEDs. Improved indium homogeneity with InGaN IL, and phase separation with A1GaN IL were observed in the light images of the LEDs.展开更多
GaN/InGaN superlattice barriers are used in InGaN-based light-emitting diodes （LEDs）. The electrostatic field in the quantum wells, electron hole wavefunction overlap, carrier concentration, spontaneous emission spe...GaN/InGaN superlattice barriers are used in InGaN-based light-emitting diodes （LEDs）. The electrostatic field in the quantum wells, electron hole wavefunction overlap, carrier concentration, spontaneous emission spectrum, light-current performance curve, and internal quantum efficiency are numerically investigated using the APSYS simulation software. It is found that the structure with GaN/InGaN superlattice barriers shows improved light output power, and lower current leakage and efficiency droop. According to our numerical simulation and analysis, these improvements in the electrical and optical characteristics are mainly attributed to the alleviation of the electrostatic field in the active region.展开更多
The efficiency enhancement of an InGaN light-emitting diode （LED） with an A1GaN/InGaN superlattice （SL） electron-blocking layer （EBL） is studied numerically, which involves the light-current performance curve, i...The efficiency enhancement of an InGaN light-emitting diode （LED） with an A1GaN/InGaN superlattice （SL） electron-blocking layer （EBL） is studied numerically, which involves the light-current performance curve, internal quan- tum efficiency electrostatic field band wavefunction, energy band diagram carrier concentration, electron current density, and radiative recombination rate. The simulation results indicate that the LED with an A1GaN/InGaN SL EBL has better optical performance than the LED with a conventional rectangular A1GaN EBL or a normal A1GaN/GaN SL EBL because of the appropriately modified energy band diagram, which is favorable ibr the injection of holes and confinement of elec- trons. Additionally, the efficiency droop of the LED with an AIGaN/InGaN SL EBL is markedly improved by reducing the polarization field in the active region.展开更多
GaN/InGaN based violet light emitting diodes (LEDs), emitting at 430 nm, have been grown on conventional single side polished (SSP) and patterned sapphire substrates (PSS). Characteristics of the epitaxial wafers and ...GaN/InGaN based violet light emitting diodes (LEDs), emitting at 430 nm, have been grown on conventional single side polished (SSP) and patterned sapphire substrates (PSS). Characteristics of the epitaxial wafers and subsequently fabricated LEDs have been analyzed. The photoluminescence (PL) peaks have been observed at 428.1 nm 426.1 nm for the epitaxial layers on SSP and PSS respectively. The PL intensity is 2.9 times higher in the case of PSS. The electroluminescence (EL) peaks have been observed at 430.78 nm and 430.35 nm for the LEDs on SSP and PSS respectively. The light output from LED fabricated on the PSS is 2.15 times higher than that of the LED on SSP at a forward current of 100 mA.展开更多
基金supported by the National Key Research and Development Program of China (2017YFE0131500, 2022YFB2802801)the National Natural Science Foundation of China (61834008, U21A20493)+1 种基金the Key Research and Development Program of Jiangsu Province (BE2020004, BE2021008-1)the Suzhou Key Laboratory of New-type Laser Display Technology (SZS2022007)
文摘The InGaN films and GaN/InGaN/GaN tunnel junctions(TJs)were grown on GaN templates with plasma-assisted molecular beam epitaxy.As the In content increases,the quality of InGaN films grown on GaN templates decreases and the surface roughness of the samples increases.V-pits and trench defects were not found in the AFM images.p++-GaN/InGaN/n++-GaN TJs were investigated for various In content,InGaN thicknesses and doping concentration in the InGaN insert layer.The InGaN insert layer can promote good interband tunneling in GaN/InGaN/GaN TJ and significantly reduce operating voltage when doping is sufficiently high.The current density increases with increasing In content for the 3 nm InGaN insert layer,which is achieved by reducing the depletion zone width and the height of the potential barrier.At a forward current density of 500 A/cm^(2),the measured voltage was 4.31 V and the differential resistance was measured to be 3.75×10^(−3)Ω·cm^(2)for the device with a 3 nm p++-In_(0.35)Ga_(0.65)N insert layer.When the thickness of the In_(0.35)Ga_(0.65)N layer is closer to the“balanced”thickness,the TJ current density is higher.If the thickness is too high or too low,the width of the depletion zone will increase and the current density will decrease.The undoped InGaN layer has a better performance than n-type doping in the TJ.Polarization-engineered tunnel junctions can enhance the functionality and performance of electronic and optoelectronic devices.
文摘Waveguide characteristics of symmetrical separate confinement heterojunction multi quantum well (SCH MQW) AlGaN/GaN/InGaN laser diode (LD) are studied by using one dimensional (1 D) transfer matrix waveguide approach.Aiming at photon confinement factor,threshold current,and power efficiency,layers design for SCH MQW LD is optimized.The optimal layers parameters are 3 periods In 0.02 Ga 0.98 N/In 0.15 Ga 0.85 N QW for active layer,In 0.1 Ga 0 9 N for waveguide layer with 90nm thick,and 120×(2 5nm/2 5nm) Al 0.25 Ga 0 75 N/GaN supper lattices for cladding layer with the laser wavelength of 396 6nm.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61274039 and 51177175)the National Basic Research Program of China(Grant Nos.2010CB923201 and 2011CB301903)+4 种基金the Ph.D.Program Foundation of the Ministry of Education of China(Grant No.20110171110021)the International Science and Technology Collaboration Program of China(Grant No.2012DFG52260)the National High Technology Research and Development Program of China(Grant No.2014AA032606)the International Science and Technology Collaboration Program of Guangdong Province,China(Grant No.2013B051000041)the Opened Fund of the State Key Laboratory on Integrated Optoelectronics(Grant No.IOSKL2014KF17)
文摘The influences of stress on the properties of InGaN/GaN multiple quantum wells （MQWs） grown on silicon substrate were investigated. The different stresses were induced by growing InGaN and A1GaN insertion layers （IL） respectively before the growth of MQWs in metal-organic chemical vapor deposition （MOCVD） system. High resolution x-ray diffrac- tion （HRXRD） and photoluminescence （PL） measurements demonstrated that the InGaN IL introduced an additional ten- sile stress in n-GaN, which released the strain in MQWs. It is helpful to increase the indium incorporation in MQWs. In comparison with MQWs without the IL, the wavelength shows a red-shift. A1GaN IL introduced a compressive stress to compensate the tensile stress, which reduces the indium composition in MQWs. PL measurement shows a blue-shift of wavelength. The two kinds of ILs were adopted to InGaN/GaN MQWs LED structures. The same wavelength shifts were also observed in the electroluminescence （EL） measurements of the LEDs. Improved indium homogeneity with InGaN IL, and phase separation with A1GaN IL were observed in the light images of the LEDs.
基金supported by the National Natural Science Foundation of China (Grant No. 51172079)the Science and Technology Program of Guangdong Province,China (Grant Nos. 2010B090400456 and 2010A081002002)the Science and Technology Program of Guangzhou City, China (Grant No. 2011J4300018)
文摘GaN/InGaN superlattice barriers are used in InGaN-based light-emitting diodes （LEDs）. The electrostatic field in the quantum wells, electron hole wavefunction overlap, carrier concentration, spontaneous emission spectrum, light-current performance curve, and internal quantum efficiency are numerically investigated using the APSYS simulation software. It is found that the structure with GaN/InGaN superlattice barriers shows improved light output power, and lower current leakage and efficiency droop. According to our numerical simulation and analysis, these improvements in the electrical and optical characteristics are mainly attributed to the alleviation of the electrostatic field in the active region.
基金Project supported by the National Natural Science Foundation of China (Grant No.61176043)the Special Funds for Provincial Strategic and Emerging Industries Projects of Guangdong,China (Grant Nos.2010A081002005,2011A081301003,and 2012A080304016)
文摘The efficiency enhancement of an InGaN light-emitting diode （LED） with an A1GaN/InGaN superlattice （SL） electron-blocking layer （EBL） is studied numerically, which involves the light-current performance curve, internal quan- tum efficiency electrostatic field band wavefunction, energy band diagram carrier concentration, electron current density, and radiative recombination rate. The simulation results indicate that the LED with an A1GaN/InGaN SL EBL has better optical performance than the LED with a conventional rectangular A1GaN EBL or a normal A1GaN/GaN SL EBL because of the appropriately modified energy band diagram, which is favorable ibr the injection of holes and confinement of elec- trons. Additionally, the efficiency droop of the LED with an AIGaN/InGaN SL EBL is markedly improved by reducing the polarization field in the active region.
文摘GaN/InGaN based violet light emitting diodes (LEDs), emitting at 430 nm, have been grown on conventional single side polished (SSP) and patterned sapphire substrates (PSS). Characteristics of the epitaxial wafers and subsequently fabricated LEDs have been analyzed. The photoluminescence (PL) peaks have been observed at 428.1 nm 426.1 nm for the epitaxial layers on SSP and PSS respectively. The PL intensity is 2.9 times higher in the case of PSS. The electroluminescence (EL) peaks have been observed at 430.78 nm and 430.35 nm for the LEDs on SSP and PSS respectively. The light output from LED fabricated on the PSS is 2.15 times higher than that of the LED on SSP at a forward current of 100 mA.
基金National Natural Science Foundation of China(No.62204127)the Natural Science Foundation of Jiangsu Province(No.BK20215093)State Key Laboratory of Luminescence and Applications(No.SKLA‒2021‒04)。
