A new approach to fabricating high-quality AlInGaN film as a lattice-matched barrier layer in multiple quantum wells（MQWs） is presented. The high-quality AlInGaN film is realized by growing the AlGaN/InGaN short per...A new approach to fabricating high-quality AlInGaN film as a lattice-matched barrier layer in multiple quantum wells（MQWs） is presented. The high-quality AlInGaN film is realized by growing the AlGaN/InGaN short period superlattices through metalorganic chemical vapor deposition, and then being used as a barrier in the MQWs. The crystalline quality of the MQWs with the lattice-matched AlInGaN barrier and that of the conventional InGaN/GaN MQWs are characterized by x-ray diffraction and scanning electron microscopy. The photoluminescence（PL） properties of the InGaN/AlInGa N MQWs are investigated by varying the excitation power density and temperature through comparing with those of the InGaN/GaN MQWs. The integral PL intensity of InGaN/AlInGaN MQWs is over 3 times higher than that of InGaN/GaN MQWs at room temperature under the highest excitation power. Temperature-dependent PL further demonstrates that the internal quantum efficiency of InGaN/AlInGaN MQWs（76.1%） is much higher than that of InGaN/GaN MQWs（21%）.The improved luminescence performance of InGaN/AlInGaN MQWs can be attributed to the distinct reduction of the barrier-well lattice mismatch and the strain-induced non-radiative recombination centers.展开更多
Undoped AlInGaN epilayers on GaN templates with different hydrogen(H_(2))and nitrogen(N_(2))carrier gas ratios(1:8,2:8,and 3:8 as samples 1,2 and 3,respectively)were grown.When the flow ratio of H_(2) and N_(2) rises ...Undoped AlInGaN epilayers on GaN templates with different hydrogen(H_(2))and nitrogen(N_(2))carrier gas ratios(1:8,2:8,and 3:8 as samples 1,2 and 3,respectively)were grown.When the flow ratio of H_(2) and N_(2) rises from 1:8 to 3:8,an indium composition decrease from 3%to 1.2%is observed while the aluminum content stays constant at any flow ratio.Due to the quantum-dot-like effect,photoluminescence intensity is enhanced in the sample with the low carrier gas flow ratio of H_(2)/N_(2).However,the potential well caused by indium uneven distribution is nonuniform,which is more severe in the sample with carrier gas flow ratio 1:8.The process of carrier transfer from shallow to deep potential wells would be more difficult to accomplish,resulting in the reduction of the photoluminescence intensity.This is found to be consistent with the carriers'lifetime with the help of time-resolved photoluminescence.展开更多
A novel kind of AlInGaN ultraviolet(UV)light-emitting diode(LED)with an embedded AlN/Al_(0.3)Ga_(0.7)N distributed Bragg reflector(DBR)is proposed to enhance light extraction efficiency(LEE).The simulation technique w...A novel kind of AlInGaN ultraviolet(UV)light-emitting diode(LED)with an embedded AlN/Al_(0.3)Ga_(0.7)N distributed Bragg reflector(DBR)is proposed to enhance light extraction efficiency(LEE).The simulation technique we adopt to calculate the LEE of LEDs is based on the theory of spontaneous emission in a layered medium,the well-known mode-matching technique and the scattering matrix approach.The AlN/Al_(0.3)Ga_(0.7)N DBR was intentionally designed to have peak reflectivity at the LED emission wavelength and the optical properties of the DBR were simulated by using the transfer matrix method.A high LEE of 45.7%at 370 nm wavelength was predicted for a proposed AlInGaN UV LED consisting of 24 periods of the AlN/Al_(0.3)Ga_(0.7)N DBR,which is 1.5 times of that of the conventional AlInGaN UV LED.The investigation shows that the AlN/Al_(0.3)Ga_(0.7)N DBR grown on GaN templates with sapphire as a substrate by MOCVD can enhance the LEE effectively and would be very promising for the fabrication of high performance GaN-based UV LEDs.展开更多
We present a two-dimensional electron gas （2DEG） charge-control mobility variation based drain cur- rent model for sheet carrier density in the channel. The model was developed for the AIInGaN/A1N/GaN high- electron...We present a two-dimensional electron gas （2DEG） charge-control mobility variation based drain cur- rent model for sheet carrier density in the channel. The model was developed for the AIInGaN/A1N/GaN high- electron-mobility transistor. The sheet carrier density model used here accounts for the independence between the Fermi levels Ef and ns along with mobility for various AI and In molefractions. This physics based ns model fully depends upon the variation of El, u0, the first subband E0, the second subband El, and as. We present a physics based analytical drain current model using ns with the minimum set of parameters. The analytical resuks obtained are compared with the experimental results for four samples with various molefraction and barrier thickness. A good agreement between the results is obtained, thus validating the model.展开更多
The ridge morphology,which is related to random atomic step meandering,appears in thick AlInGaN films grown by metal organic chemical vapor deposition on both GaN templates and free-standing GaN substrates;this can be...The ridge morphology,which is related to random atomic step meandering,appears in thick AlInGaN films grown by metal organic chemical vapor deposition on both GaN templates and free-standing GaN substrates;this can be primarily attributed to the in-plane compressive strain in the thick layer.Therefore,a 2.5-μm Al 0.08 In 0.0123 GaN film with a slightly tensive strain was grown,with a regular and smooth step-flow morphology;the root mean square deviation of the film(with a size of 5μm×5μm)was 0.56 nm.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.61274003,61422401,51461135002,and 61334009)the Natural Science Foundation of Jiangsu Province,China(Grant Nos.BY2013077,BK20141320,BE2015111,and BK20161324)+1 种基金the Program for New Century Excellent Talents in University,China(Grant No.NCET-11-0229)the Special Semiconductor Materials and Devices Research Funds from State Grid Shandong Electric Power Company,China
文摘A new approach to fabricating high-quality AlInGaN film as a lattice-matched barrier layer in multiple quantum wells（MQWs） is presented. The high-quality AlInGaN film is realized by growing the AlGaN/InGaN short period superlattices through metalorganic chemical vapor deposition, and then being used as a barrier in the MQWs. The crystalline quality of the MQWs with the lattice-matched AlInGaN barrier and that of the conventional InGaN/GaN MQWs are characterized by x-ray diffraction and scanning electron microscopy. The photoluminescence（PL） properties of the InGaN/AlInGa N MQWs are investigated by varying the excitation power density and temperature through comparing with those of the InGaN/GaN MQWs. The integral PL intensity of InGaN/AlInGaN MQWs is over 3 times higher than that of InGaN/GaN MQWs at room temperature under the highest excitation power. Temperature-dependent PL further demonstrates that the internal quantum efficiency of InGaN/AlInGaN MQWs（76.1%） is much higher than that of InGaN/GaN MQWs（21%）.The improved luminescence performance of InGaN/AlInGaN MQWs can be attributed to the distinct reduction of the barrier-well lattice mismatch and the strain-induced non-radiative recombination centers.
基金Supported by the National High-Technology Research and Development Program of China under Grant No 2011AA03A105.
文摘Undoped AlInGaN epilayers on GaN templates with different hydrogen(H_(2))and nitrogen(N_(2))carrier gas ratios(1:8,2:8,and 3:8 as samples 1,2 and 3,respectively)were grown.When the flow ratio of H_(2) and N_(2) rises from 1:8 to 3:8,an indium composition decrease from 3%to 1.2%is observed while the aluminum content stays constant at any flow ratio.Due to the quantum-dot-like effect,photoluminescence intensity is enhanced in the sample with the low carrier gas flow ratio of H_(2)/N_(2).However,the potential well caused by indium uneven distribution is nonuniform,which is more severe in the sample with carrier gas flow ratio 1:8.The process of carrier transfer from shallow to deep potential wells would be more difficult to accomplish,resulting in the reduction of the photoluminescence intensity.This is found to be consistent with the carriers'lifetime with the help of time-resolved photoluminescence.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11074082 , 1147014.
文摘A novel kind of AlInGaN ultraviolet(UV)light-emitting diode(LED)with an embedded AlN/Al_(0.3)Ga_(0.7)N distributed Bragg reflector(DBR)is proposed to enhance light extraction efficiency(LEE).The simulation technique we adopt to calculate the LEE of LEDs is based on the theory of spontaneous emission in a layered medium,the well-known mode-matching technique and the scattering matrix approach.The AlN/Al_(0.3)Ga_(0.7)N DBR was intentionally designed to have peak reflectivity at the LED emission wavelength and the optical properties of the DBR were simulated by using the transfer matrix method.A high LEE of 45.7%at 370 nm wavelength was predicted for a proposed AlInGaN UV LED consisting of 24 periods of the AlN/Al_(0.3)Ga_(0.7)N DBR,which is 1.5 times of that of the conventional AlInGaN UV LED.The investigation shows that the AlN/Al_(0.3)Ga_(0.7)N DBR grown on GaN templates with sapphire as a substrate by MOCVD can enhance the LEE effectively and would be very promising for the fabrication of high performance GaN-based UV LEDs.
文摘We present a two-dimensional electron gas （2DEG） charge-control mobility variation based drain cur- rent model for sheet carrier density in the channel. The model was developed for the AIInGaN/A1N/GaN high- electron-mobility transistor. The sheet carrier density model used here accounts for the independence between the Fermi levels Ef and ns along with mobility for various AI and In molefractions. This physics based ns model fully depends upon the variation of El, u0, the first subband E0, the second subband El, and as. We present a physics based analytical drain current model using ns with the minimum set of parameters. The analytical resuks obtained are compared with the experimental results for four samples with various molefraction and barrier thickness. A good agreement between the results is obtained, thus validating the model.
基金supported by National Natural Science Foundation of China(Grants No.61834008,61574160,61804164 and 61704184)National Key Research and Development Program of China(Grants No.2017YFE0131500 and 2017YFB0405000)+2 种基金Natural Science Foundation of Jiangsu Province(Grant No.BK20180254)Key Research and Devel-opment Program of Jiangsu Province(Grant No.BE2020004)China Postdoctoral Science Foundation(Grant No.2018M630619).
文摘The ridge morphology,which is related to random atomic step meandering,appears in thick AlInGaN films grown by metal organic chemical vapor deposition on both GaN templates and free-standing GaN substrates;this can be primarily attributed to the in-plane compressive strain in the thick layer.Therefore,a 2.5-μm Al 0.08 In 0.0123 GaN film with a slightly tensive strain was grown,with a regular and smooth step-flow morphology;the root mean square deviation of the film(with a size of 5μm×5μm)was 0.56 nm.
基金National Natural Science Foundation of China(60477011,60776042)National Basic Research Program of China( 2006CB604908,2006CB921607 )+1 种基金the National High Technology Program of China(2007AA03Z403)“973”Project (2007CB307004)~~
