具有渐变量子垒的氮极性AlGaN基LED实现载流子调控和性能增强（英文）
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摘要
为了获得高效率的AlGaN基深紫外发光二极管,提出了具有渐变量子垒的氮极性结构来调控载流子的传输.通过氮极性结构在p型电子阻挡层中形成的反向极化诱导势垒,改善空穴注入和电子泄漏问题.另外研究了不同的渐变方向和渐变程度对器件性能的影响.模拟结果显示,在12nm的AlGaN量子垒上沿着(000-1)方向从Al组分0.65线性渐变到0.6,可以有效平衡量子垒的势垒高度和斜率,从而极大的增强空穴注入,光输出功率相较于传统结构提高了53.6%.该设计为电子泄漏和空穴注入问题提供了直接而有效的解决方案,在实现更高效率的深紫外发光二极管方面显示出广阔的前景.
To achieve efficient AlGaN-based Deep Ultraviolet Light-Emitting Diode(DUV LED),the Npolar LED structure with grading quantum barriers is proposed to manipulate the carrier transport.By adopting the N-polar structure,the hole injection and the electron overflow issues can be improved due to the reversed polarization-induced potential barrier for carrier transport in p-type electron blocking layer.Furthermore,the impacts of different grading directions and schemes on the device performance are investigated.Simulation results show that grading the Al composition linearly from 0.65 to 0.6 for the12 nm-thick AlGaN quantum barriers along the(000-1)can well balance the quantum barrier height and slope,thus resulting in remarkable improvement of hole injection as well as 53.6% enhancement of optical output power.The proposed design provides a straightforward and effective solution to the electron overflow and hole injection issues,which shows promise in the pursuit of higher efficiency DUV LED.
To achieve efficient AlGaN-based Deep Ultraviolet Light-Emitting Diode(DUV LED),the Npolar LED structure with grading quantum barriers is proposed to manipulate the carrier transport.By adopting the N-polar structure,the hole injection and the electron overflow issues can be improved due to the reversed polarization-induced potential barrier for carrier transport in p-type electron blocking layer.Furthermore,the impacts of different grading directions and schemes on the device performance are investigated.Simulation results show that grading the Al composition linearly from 0.65 to 0.6 for the12 nm-thick AlGaN quantum barriers along the(000-1)can well balance the quantum barrier height and slope,thus resulting in remarkable improvement of hole injection as well as 53.6% enhancement of optical output power.The proposed design provides a straightforward and effective solution to the electron overflow and hole injection issues,which shows promise in the pursuit of higher efficiency DUV LED.
引文
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[26]DENG G,ZHANG Y,YU Y,et al.Significantly improved surface morphology of N-polar GaN film grown on SiCsubstrate by the optimization of V/III ratio[J].Applied Physics Letters,2018,112(15):151607.
[27]KELLER S,FICHTENBAUM N,WU F,et al.Influence of the substrate misorientation on the properties of N-polar GaN films grown by metal organic chemical vapor deposition[J].Journal of Applied Physics,2007,102(8):083546.
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[29]FICHTENBAUM N,MATES T,KELLER S,et al.Impurity incorporation in heteroepitaxial N-face and Ga-face GaNfilms grown by metalorganic chemical vapor deposition[J].Journal of Crystal Growth,2008,310(6):1124-1131.
[30]SIMON J,PROTASENKO V,LIAN C,et al.Polarization-induced hole doping in wide-band-gap uniaxial semiconductor heterostructures[J].Science,2010,327(5961):60-64.
[31]YAN L,ZHANG Y,HAN X,et al.Polarization-induced hole doping in N-polar III-nitride LED grown by metalorganic chemical vapor deposition[J].Applied Physics Letters,2018,112(18):182104.
[32]BAO X,SUN P,LIU S,et al.Performance improvements for AlGaN-based deep ultraviolet light-emitting diodes with the p-type and thickened last quantum barrier[J].IEEE Photonics Journal,2015,7(1):1-10.
[33]CHEN S,LI Y,TIAN W,et al.Numerical analysis on the effects of multi-quantum last barriers in AlGaN-based ultraviolet light-emitting diodes[J].Applied Physics A,2015,118(4):1357-1363.
[34]CHANG J Y,CHANG H T,SHIH Y H,et al.Efficient carrier confinement in deep-ultraviolet light-emitting diodes with composition-graded configuration[J].IEEE Transactions on Electron Devices,2017,64(12):4980-4984.
[35]MANUAL A U S.Crosslight software inc[M].Burnaby,BC,Canada,2013.
[36]BERNARDINI F,FIORENTINI V,VANDERBILT D.Spontaneous polarization and piezoelectric constants of III-Vnitrides[J].Physical Review B,1997,56(16):R10024.
[37]FIORENTINI V,BERNARDINI F,AMBACHER O.Evidence for nonlinear macroscopic polarization in III-V nitride alloy heterostructures[J].Applied Physics Letters,2002,80(7):1204-1206.
[38]COUGHLAN C,SCHULZ S,CARO M A,et al.Band gap bowing and optical polarization switching in Al Ga N alloys[J].Physica Status Solidi B,2015,252(5):879-884.
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[40]NAKARMI M,KIM K,KHIZAR M,et al.Electrical and optical properties of Mg-doped Al 0.7Ga 0.3Nalloys[J].Applied Physics Letters,2005,86(9):092108.
[41]TURIN V O.A modified transferred-electron high-field mobility model for GaN devices simulation[J].Solid-State Electronics,2005,49(10):1678-1682.
[42]CANALI C,MAJNI G,MINDER R,et al.Electron and hole drift velocity measurements in silicon and their empirical relation to electric field and temperature[J].IEEE Transactions on Electron Devices,1975,22(11):1045-1047.
[43]KINOSHITA T,OBATA T,YANAGI H,et al.High p-type conduction in high-Al content Mg-doped AlGaN[J].Applied Physics Letters,2013,102(1):012105.
[44]KOZODOY P,XING H,DENBAARS S P,et al.Heavy doping effects in Mg-doped GaN[J].Journal of Applied Physics,2000,87(4):1832-1835.
[45]PUNYA A,LAMBRECHT W R.Valence band effective-mass Hamiltonians for the group-III nitrides from quasiparticle self-consistent G W band structures[J].Physical Review B,2012,85(19):195147.
[46]YUN J,SHIM J I,HIRAYAMA H.Analysis of efficiency droop in 280-nm AlGaN multiple-quantum-well lightemitting diodes based on carrier rate equation[J].Applied Physics Express,2015,8(2):022104.
[47]PIPREK J,FARRELL R,DENBAARS S,et al.Effects of built-in polarization on InGaN-GaN vertical-cavity surfaceemitting lasers[J].IEEE Photonics Technology Letters,2006,18(1):7-9.
[48]NAKARMI M,NEPAL N,LIN J,et al.Photoluminescence studies of impurity transitions in Mg-doped AlGaN alloys[J].Applied Physics Letters,2009,94(9):091903.
[49]VERZELLESI G,SAGUATTI D,MENEGHINI M,et al.Efficiency droop in InGaN/GaN blue light-emitting diodes:Physical mechanisms and remedies[J].Journal of Applied Physics,2013,114(7):10.
[50]ZAUNER A,WEYHER J,PLOMP M,et al.Homo-epitaxial GaN growth on exact and misoriented single crystals:suppression of hillock formation[J].Journal of Crystal Growth,2000,210(4):435-443.
[51]ZAUNER A,ARET E,VAN ENCKEVORT W,et al.Homo-epitaxial growth on the N-face of GaN single crystals:the influence of the misorientation on the surface morphology[J].Journal of Crystal Growth,2002,240(1-2):14-21.
[52]TAKEUCHI M,SHIMIZU H,KAJITANI R,et al.Al-and N-polar AlN layers grown on c-plane sapphire substrates by modified flow-modulation MOCVD[J].Journal of Crystal Growth,2007,305(2):360-365.
[53]WU Y,HANLON A,KAEDING J,et al.Effect of nitridation on polarity,microstructure,and morphology of AlNfilms[J].Applied Physics Letters,2004,84(6):912-914.
[54]SONG J,YUAN G,XIONG K,et al.Epitaxial lateral overgrowth of nitrogen-polar(0001)GaN by metalorganic chemical vapor deposition[J].Crystal Growth&Design,2014,14(5):2510-2515.
[55]STOLYARCHUK N,MARKURT T,COURVILLE A,et al.Impact of sapphire nitridation on formation of Al-polar inversion domains in N-polar AlN epitaxial layers[J].Journal of Applied Physics,2017,122(15):155303.
[56]KUELLER V,KNAUER A,BRUNNER F,et al.Investigation of inversion domain formation in AlN grown on sapphire by MOVPE[J].Physica Status Solidi C,2012,9(3-4):496-498.
[57]KIM H,RYOU J H,DUPUIS R D,et al.Electrical characteristics of contacts to thin film N-polar n-type GaN[J].Applied Physics Letters,2008,93(19):192106.
[58]DASGUPTA S,NIDH I,BROWN D F,et al.Ultralow nonalloyed ohmic contact resistance to self aligned N-polar GaN high electron mobility transistors by In(Ga)N regrowth[J].Applied Physics Letters,2010,96(14):143504.
[59]LIU J,FENG F,ZHOU Y,et al.Stability of Al/Ti/Au contacts to N-polar n-GaN of GaN based vertical light emitting diode on silicon substrate[J].Applied Physics Letters,2011,99(11):111112.
[60]PTAK A,HOLBERT L,TING L,et al.Controlled oxygen doping of GaN using plasma assisted molecular-beam epitaxy[J].Applied Physics Letters,2001,79(17):2740-2742.
[2]PARK J-S,KIM J K,CHO J,et al.Review-group III-nitride-based ultraviolet light-emitting diodes:ways of increasing external quantum efficiency[J].Ecs Journal of Solid State Science and Technology,2017,6(4):Q42-Q52.
[3]KHAN A,BALAKRISHNAN K,KATONA T.Ultraviolet light-emitting diodes based on group three nitrides[J].Nature Photonics,2008,2(2):77-84.
[4]KNEISSL M,KOLBE T,CHUA C,et al.Advances in group III-nitride-based deep UV light-emitting diode technology[J].Semiconductor Science and Technology,2011,26(1):014036.
[5]TAKANO T,MINO T,SAKAI J,et al.Deep-ultraviolet light-emitting diodes with external quantum efficiency higher than 20%at 275nm achieved by improving light-extraction efficiency[J].Applied Physics Express,2017,10(3):031002.
[6]SZE S M,NG K K.Physics of semiconductor devices[M].John Wiley&Sons,2006.
[7]SHERVIN S,OH S K,PARK H J,et al.Flexible deep-ultraviolet light-emitting diodes for significant improvement of quantum efficiencies by external bending[J].Journal of Physics D:Applied Physics,2018,51(10):105105.
[8]KIM M H,SCHUBERT M F,DAI Q,et al.Origin of efficiency droop in GaN-based light-emitting diodes[J].Applied Physics Letters,2007,91(18):183507.
[9]KUO Y K,CHANG J Y,TSAI M C.Enhancement in hole-injection efficiency of blue InGaN light-emitting diodes from reduced polarization by some specific designs for the electron blocking layer[J].Optics Letters,2010,35(19):3285-3287.
[10]HIRAYAMA H,TSUKADA Y,MAEDA T,et al.Marked enhancement in the efficiency of deep-ultraviolet AlGaNlight-emitting diodes by using a multiquantum-barrier electron blocking layer[J].Applied Physics Express,2010,3(3):031002.
[11]REN Z,LU Y,YAO H H,et al.III-nitride deep UV LED without electron blocking layer[J].IEEE Photonics Journal,2019,11(2):8200511.
[12]LI L,ZHANG Y,XU S,et al.On the hole injection for III-nitride based deep ultraviolet light-emitting diodes[J].Materials,2017,10(10):1221.
[13]ZHANG Z H,HUANG CHEN S W,ZHANG Y,et al.Hole transport manipulation to improve the hole injection for deep ultraviolet light-emitting diodes[J].Acs Photonics,2017,4(7):1846-1850.
[14]ZHANG Y,YU L,LI K,et al.The improvement of deep-ultraviolet light-emitting diodes with gradually decreasing Al content in AlGaN electron blocking layers[J].Superlattices and Microstructures,2015,82:151-157.
[15]FAN X,SUN H,LI X,et al.Efficiency improvements in AlGaN-based deep ultraviolet light-emitting diodes using inverted-V-shaped graded Al composition electron blocking layer[J].Superlattices and Microstructures,2015,88:467-473.
[16]YIN Y A,WANG N,LI S,et al.Advantages of deep-UV AlGaN light-emitting diodes with an AlGaN/AlGaNsuperlattices electron blocking layer[J].Applied Physics A,2015,119(1):41-44.
[17]ZHANG Z H,CHEN S W H,CHU C,et al.Nearly efficiency-droop-free AlGaN-based ultraviolet light-emitting diodes with a specifically designed superlattice p-type electron blocking layer for high mg doping efficiency[J].Nanoscale Research Letters,2018,13(1):122.
[18]JANJUA B,NG T K,ALYAMANI A Y,et al.Enhancing carrier injection using graded superlattice electron blocking layer for UVB light-emitting diodes[J].IEEE Photonics Journal,2014,6(6):1-12.
[19]ZHANG X,SUN H,HUANG J,et al.Efficiency improvements in AlGaN-based deep-ultraviolet light-emitting diodes with graded superlattice last quantum barrier and without electron blocking layer[J].Journal of Electronic Materials,2019,48(7):460-466.
[20]MASUI H,KELLER S,FELLOWS N,et al.Luminescence characteristics of N-Polar GaN and InGaN films grown by metal organic chemical vapor deposition[J].Japanese Journal of Applied Physics,2009,48(7R):071003.
[21]AKYOL F,NATH D N,GR E,et al.N-polar III-nitride green(540nm)light emitting diode[J].Japanese Journal of Applied Physics,2011,50(5R):052101.
[22]FENG S W,LIAO P H,LEUNG B,et al.Efficient carrier relaxation and fast carrier recombination of N-polar InGaN/GaN light emitting diodes[J].Journal of Applied Physics,2015,118(4):043104.
[23]AKYOL F,NATH D,KRISHNAMOORTHY S,et al.Suppression of electron overflow and efficiency droop in N-polar GaN green light emitting diodes[J].Applied Physics Letters,2012,100(11):111118.
[24]VERMA J,SIMON J,PROTASENKO V,et al.N-polar III-nitride quantum well light-emitting diodes with polarization-induced doping[J].Applied Physics Letters,2011,99(17):171104.
[25]WON D,WENG X,REDWING J M.Metalorganic chemical vapor deposition of N-polar GaN films on vicinal SiCsubstrates using indium surfactants[J].Applied Physics Letters,2012,100(2):021913.
[26]DENG G,ZHANG Y,YU Y,et al.Significantly improved surface morphology of N-polar GaN film grown on SiCsubstrate by the optimization of V/III ratio[J].Applied Physics Letters,2018,112(15):151607.
[27]KELLER S,FICHTENBAUM N,WU F,et al.Influence of the substrate misorientation on the properties of N-polar GaN films grown by metal organic chemical vapor deposition[J].Journal of Applied Physics,2007,102(8):083546.
[28]ZYWIETZ T K,NEUGEBAUER J,SCHEFFLER M.The adsorption of oxygen at GaN surfaces[J].Applied Physics Letters,1999,74(12):1695-1697.
[29]FICHTENBAUM N,MATES T,KELLER S,et al.Impurity incorporation in heteroepitaxial N-face and Ga-face GaNfilms grown by metalorganic chemical vapor deposition[J].Journal of Crystal Growth,2008,310(6):1124-1131.
[30]SIMON J,PROTASENKO V,LIAN C,et al.Polarization-induced hole doping in wide-band-gap uniaxial semiconductor heterostructures[J].Science,2010,327(5961):60-64.
[31]YAN L,ZHANG Y,HAN X,et al.Polarization-induced hole doping in N-polar III-nitride LED grown by metalorganic chemical vapor deposition[J].Applied Physics Letters,2018,112(18):182104.
[32]BAO X,SUN P,LIU S,et al.Performance improvements for AlGaN-based deep ultraviolet light-emitting diodes with the p-type and thickened last quantum barrier[J].IEEE Photonics Journal,2015,7(1):1-10.
[33]CHEN S,LI Y,TIAN W,et al.Numerical analysis on the effects of multi-quantum last barriers in AlGaN-based ultraviolet light-emitting diodes[J].Applied Physics A,2015,118(4):1357-1363.
[34]CHANG J Y,CHANG H T,SHIH Y H,et al.Efficient carrier confinement in deep-ultraviolet light-emitting diodes with composition-graded configuration[J].IEEE Transactions on Electron Devices,2017,64(12):4980-4984.
[35]MANUAL A U S.Crosslight software inc[M].Burnaby,BC,Canada,2013.
[36]BERNARDINI F,FIORENTINI V,VANDERBILT D.Spontaneous polarization and piezoelectric constants of III-Vnitrides[J].Physical Review B,1997,56(16):R10024.
[37]FIORENTINI V,BERNARDINI F,AMBACHER O.Evidence for nonlinear macroscopic polarization in III-V nitride alloy heterostructures[J].Applied Physics Letters,2002,80(7):1204-1206.
[38]COUGHLAN C,SCHULZ S,CARO M A,et al.Band gap bowing and optical polarization switching in Al Ga N alloys[J].Physica Status Solidi B,2015,252(5):879-884.
[39]COLLAZO R,MITA S,XIE J,et al.Progress on n-type doping of AlGaN alloys on AlN single crystal substrates for UV optoelectronic applications[J].Physica Status Solidi C,2011,8(7-8):2031-2033.
[40]NAKARMI M,KIM K,KHIZAR M,et al.Electrical and optical properties of Mg-doped Al 0.7Ga 0.3Nalloys[J].Applied Physics Letters,2005,86(9):092108.
[41]TURIN V O.A modified transferred-electron high-field mobility model for GaN devices simulation[J].Solid-State Electronics,2005,49(10):1678-1682.
[42]CANALI C,MAJNI G,MINDER R,et al.Electron and hole drift velocity measurements in silicon and their empirical relation to electric field and temperature[J].IEEE Transactions on Electron Devices,1975,22(11):1045-1047.
[43]KINOSHITA T,OBATA T,YANAGI H,et al.High p-type conduction in high-Al content Mg-doped AlGaN[J].Applied Physics Letters,2013,102(1):012105.
[44]KOZODOY P,XING H,DENBAARS S P,et al.Heavy doping effects in Mg-doped GaN[J].Journal of Applied Physics,2000,87(4):1832-1835.
[45]PUNYA A,LAMBRECHT W R.Valence band effective-mass Hamiltonians for the group-III nitrides from quasiparticle self-consistent G W band structures[J].Physical Review B,2012,85(19):195147.
[46]YUN J,SHIM J I,HIRAYAMA H.Analysis of efficiency droop in 280-nm AlGaN multiple-quantum-well lightemitting diodes based on carrier rate equation[J].Applied Physics Express,2015,8(2):022104.
[47]PIPREK J,FARRELL R,DENBAARS S,et al.Effects of built-in polarization on InGaN-GaN vertical-cavity surfaceemitting lasers[J].IEEE Photonics Technology Letters,2006,18(1):7-9.
[48]NAKARMI M,NEPAL N,LIN J,et al.Photoluminescence studies of impurity transitions in Mg-doped AlGaN alloys[J].Applied Physics Letters,2009,94(9):091903.
[49]VERZELLESI G,SAGUATTI D,MENEGHINI M,et al.Efficiency droop in InGaN/GaN blue light-emitting diodes:Physical mechanisms and remedies[J].Journal of Applied Physics,2013,114(7):10.
[50]ZAUNER A,WEYHER J,PLOMP M,et al.Homo-epitaxial GaN growth on exact and misoriented single crystals:suppression of hillock formation[J].Journal of Crystal Growth,2000,210(4):435-443.
[51]ZAUNER A,ARET E,VAN ENCKEVORT W,et al.Homo-epitaxial growth on the N-face of GaN single crystals:the influence of the misorientation on the surface morphology[J].Journal of Crystal Growth,2002,240(1-2):14-21.
[52]TAKEUCHI M,SHIMIZU H,KAJITANI R,et al.Al-and N-polar AlN layers grown on c-plane sapphire substrates by modified flow-modulation MOCVD[J].Journal of Crystal Growth,2007,305(2):360-365.
[53]WU Y,HANLON A,KAEDING J,et al.Effect of nitridation on polarity,microstructure,and morphology of AlNfilms[J].Applied Physics Letters,2004,84(6):912-914.
[54]SONG J,YUAN G,XIONG K,et al.Epitaxial lateral overgrowth of nitrogen-polar(0001)GaN by metalorganic chemical vapor deposition[J].Crystal Growth&Design,2014,14(5):2510-2515.
[55]STOLYARCHUK N,MARKURT T,COURVILLE A,et al.Impact of sapphire nitridation on formation of Al-polar inversion domains in N-polar AlN epitaxial layers[J].Journal of Applied Physics,2017,122(15):155303.
[56]KUELLER V,KNAUER A,BRUNNER F,et al.Investigation of inversion domain formation in AlN grown on sapphire by MOVPE[J].Physica Status Solidi C,2012,9(3-4):496-498.
[57]KIM H,RYOU J H,DUPUIS R D,et al.Electrical characteristics of contacts to thin film N-polar n-type GaN[J].Applied Physics Letters,2008,93(19):192106.
[58]DASGUPTA S,NIDH I,BROWN D F,et al.Ultralow nonalloyed ohmic contact resistance to self aligned N-polar GaN high electron mobility transistors by In(Ga)N regrowth[J].Applied Physics Letters,2010,96(14):143504.
[59]LIU J,FENG F,ZHOU Y,et al.Stability of Al/Ti/Au contacts to N-polar n-GaN of GaN based vertical light emitting diode on silicon substrate[J].Applied Physics Letters,2011,99(11):111112.
[60]PTAK A,HOLBERT L,TING L,et al.Controlled oxygen doping of GaN using plasma assisted molecular-beam epitaxy[J].Applied Physics Letters,2001,79(17):2740-2742.