掺Fe高阻GaN缓冲层特性及其对AlGaN/GaN高电子迁移率晶体管器件的影响研究

利用金属有机物化学气相沉积技术在蓝宝石衬底上制备了掺Fe高阻Ga N以及Al Ga N/Ga N高电子迁移率晶体管(HEMT)结构.对Cp_2Fe流量不同的高阻Ga N特性进行了研究.研究结果表明,Fe杂质在Ga N材料中引入的Fe~(3+/2+)深受主能级能够补偿背景载流子浓度从而实现高阻,Fe杂质在Ga N材料中引入更多起受主作用的刃位错,也在一定程度上补偿了背景载流子浓度.在一定范围内,Ga N材料方块电阻随Cp_2Fe流量增加而增加,Cp_2Fe流量为100 sccm(1 sccm 1mL min)时,方块电阻增加不再明显;另外增加Cp_2Fe流量也会导致材料质量下降,表面更加粗糙.因此,优选Cp_2Fe流量为75 sccm,相应方块电阻高达×10?/,外延了不同掺Fe层厚度的Al Ga N/Ga N HEMT结构,并制备成器件.HEMT器件均具有良好的夹断以及栅控特性,并且增加掺Fe层厚度使得HEMT器件的击穿电压提高了39.3%,同时对器件的转移特性影响较小.     

结构参数对N极性面GaN/InAlN高电子迁移率晶体管性能的影响

基于漂移-扩散传输模型、费米狄拉克统计模型以及Shockley-Read-Hall复合模型等,通过自洽求解薛定谔方程、泊松方程以及载流子连续性方程,模拟研究了材料结构参数对N极性面GaN/InAlN高电子迁移率晶体管性能的影响及其物理机制.结果表明,增加GaN沟道层的厚度(5—15 nm)与InAlN背势垒层的厚度(10—40 nm),均使得器件的饱和输出电流增大,阈值电压发生负向漂移.器件的跨导峰值随Ga N沟道层厚度的增加与InAlN背势垒层厚度的减小而减小.模拟中,各种性能参数的变化趋势均随GaN沟道层与InAlN背势垒层厚度的增加而逐渐变缓,当GaN沟道层厚度超过15 nm、InAlN背势垒层厚度超过40 nm后,器件的饱和输出电流、阈值电压等参数基本趋于稳定.材料结构参数对器件性能影响的主要原因可归于器件内部极化效应、能带结构以及沟道中二维电子气的变化.     

具有高阈值电压和大栅压摆幅的常关型槽栅AlGaN/GaN金属氧化物半导体高电子迁移率晶体管（英文）

介绍了一种具有高阈值电压和大栅压摆幅的常关型槽栅AlGaN/GaN金属氧化物半导体高电子迁移率晶体管。采用原子层淀积(ALD)方法实现Al_2O_3栅介质的沉积。槽栅常关型AlGaN/GaN MOS-HEMT的栅长(Lg)为2μm,栅宽(Wg)为0.9 mm(0.45 mm×2),栅极和源极(Lgs)之间的距离为5μm,栅极和漏极(Lgd)之间的距离为10μm。在栅压为-20 V时,槽栅常关型AlGaN/GaN MOS-HEMT的栅漏电仅为0.65 nA。在栅压为+12 V时,槽栅常关型AlGaN/GaN MOS-HEMT的栅漏电为225 nA。器件的栅压摆幅为-20~+12V。在栅压V_(gs)=+10 V时,槽栅常关型AlGaN/GaN MOS-HEMT电流和饱和电流密度分别达到了98 mA和108 mA/mm(Wg=0.9 mm),特征导通电阻为4 mΩ·cm2。槽栅常关型AlGaN/GaN MOS-HEMT的阈值电压为+4.6 V,开启与关断电流比达到了5×108。当V_(ds)=7 V时,器件的峰值跨导为42 mS/mm(Wg=0.9 mm,V_(gs)=+10 V)。在V_(gs)=0 V时,栅漏间距为10μm的槽栅常关型AlGaN/GaN MOS-HEMT的关断击穿电压为450 V,关断泄露电流为0.025 mA/mm。     

具有部分本征GaN帽层新型AlGaN/GaN高电子迁移率晶体管特性分析

为了优化传统Al GaN/GaN高电子迁移率晶体管(high electron mobility transistors,HEMTs)器件的表面电场,提高击穿电压,本文提出了一种具有部分本征GaN帽层的新型Al GaN/GaN HEMTs器件结构.新型结构通过在Al GaN势垒层顶部、栅电极到漏电极的漂移区之间引入部分本征GaN帽层,由于本征GaN帽层和Al GaN势垒层界面处的极化效应,降低了沟道二维电子气(two dimensional electron gas,2DEG)的浓度,形成了栅边缘低浓度2DEG区域,使得沟道2DEG浓度分区,由均匀分布变为阶梯分布.通过调制沟道2DEG的浓度分布,从而调制了Al GaN/GaN HEMTs器件的表面电场.利用电场调制效应,产生了新的电场峰,且有效降低了栅边缘的高峰电场,Al GaN/GaN HEMTs器件的表面电场分布更加均匀.利用ISE-TCAD软件仿真分析得出:通过设计一定厚度和长度的本征GaN帽层,Al GaN/GaN HEMTs器件的击穿电压从传统结构的427 V提高到新型结构的960 V.由于沟道2DEG浓度减小,沟道电阻增加,使得新型Al GaN/GaN HEMTs器件的最大输出电流减小了9.2%,截止频率几乎保持不变,而最大振荡频率提高了12%.     

808nm边发射二极管激光器特征温度

研究了波导层材料为Al0.65Ga0.35As时的3种不同厚度(0.4,0.5和0.6μm)和3种不同的Al GaAs基大光学腔(Al0.65Ga0.35As-1μm,Al0.6Ga0.4As-1.5μm和Al0.45Ga0.55As-2μm)的808 nm边发射二极管激光器的输出特性。理论计算模拟了不同结构器件的功率-电流特性(P-I)曲线,采用线性拟合的方法计算阈值电流,并计算了器件的特征温度。实验结果验证了理论计算结果。波导层厚度变化的研究说明,当单量子阱的厚度不变时,波导层越厚,器件的特征温度越高,器件的性能也就越好。大光学腔变化的研究表明,由于Al的组分x=0.45时会产生有效的垂直光斑尺寸和更低的电阻,使得2μm-LOC结构的器件性能最好。     

具有高开启/关断电流比的Al_2O_3/AlGaN/GaN金属氧化物半导体高电子迁移率晶体管（英文）

采用原子层淀积(ALD)方法,制备了Al_2O_3为栅介质的高性能AlG aN/GaN金属氧化物半导体高电子迁移率晶体管(MOS-HEMT)。在栅压为-20 V时,MOS-HEMT的栅漏电比Schottky-gate HEMT的栅漏电低4个数量级以上。在栅压为+2 V时,Schottky-gate HEMT的栅漏电为191μA;在栅压为+20 V时,MOS-HEMT的栅漏电仅为23.6 nA,比同样尺寸的Schottky-gate HEMT的栅漏电低将近7个数量级。AlG aN/GaN MOSHEMT的栅压摆幅达到了±20 V。在栅压Vgs=0 V时,MOS-HEMT的饱和电流密度达到了646 mA/mm,相比Schottky-gate HEMT的饱和电流密度(277 mA/mm)提高了133%。栅漏间距为10μm的AlG aN/GaN MOSHEMT器件在栅压为+3 V时的最大饱和输出电流达到680 mA/mm,特征导通电阻为1.47 mΩ·cm2。Schottky-gate HEMT的开启与关断电流比仅为105,MOS-HEMT的开启与关断电流比超过了109,超出了Schottkygate HEMT器件4个数量级,原因是栅漏电的降低提高了MOS-HEMT的开启与关断电流比。在Vgs=-14 V时,栅漏间距为10μm的AlG aN/GaN MOS-HEMT的关断击穿电压为640 V,关断泄露电流为27μA/mm。     

MMIC LNA based novel composite-channel Al0.3Ga0.7N/Al0.05Ga0.95N/GaN HEMTs

A microwave monolithic integrated circuit （MMIC） C-band low noise amplifier （LNA） using 1 μm-gate composite-channel Al0.3Ga0.7N/Al0.05Ga0.95N/GaN high electron mobility transistors （CC-HEMTs） has been designed, fabricated and characterized. The material structure and special channel of CC-HEMT were given and analysed. The MMIC LNA with CC-HEMT showed a noise figure of 2.4 dB, an associated gain of 12.3 dB, an input return loss of -6 dB and an output return loss of -16 dB at 6GHz. The IIP3 of the LNA is 13 dBm at 6 GHz. The LNA with 1 μm ×100 μm device showed very high-dynamic range with decent gain and noise figure.[第一段]     

1 μm波段高功率超辐射发光二极管

为提高1μm波段超辐射发光二极管的输出特性,对外延结构及J型波导结构参数进行研究,基于研究结果确定外延结构及波导结构参数并对电极窗口制备工艺及单层氧化铪薄膜成膜条件进行了优化。研究表明,缩小波导与限制层AlGaAs材料中Al组分差值利于改善器件光束特性。此外,增加刻蚀深度、脊宽及曲率半径均会使损耗系数减小以提高器件输出功率。基于仿真结果制备出非均匀阱宽大阱深的三量子阱结构器件,前腔面镀制反射率约为0.5%的单层氧化铪薄膜,后腔面蒸镀高反膜,腔长约2 mm,波导曲率半径为21.8mm,在500 mA连续电流注入下,实现了118.1 mW输出功率和32.5 nm光谱半宽。单层增透膜的设计抑制了器件激射并简化了工艺复杂度,避免了多层增透膜不同材料间的应力问题。     

透明衬底光致导电网栅的设计与制作

依据半导体光电导效应分析了光致导电复合网栅调控机理,阐明了光致导电复合网栅的设计思路与结构特点.结合透明衬底蓝宝石基片,选取雷达波2~18GHz,红外3~12μm波段为研究对象对复合网栅结构参数进行优化和仿真,当网栅参数周期由5mm变为2.5mm、边长由4.9mm变为2.4mm时,网栅的中心谐振频率从13.2GHz变为14GHz.采用衍射光栅同轴对准原理保证两次lift-off光刻工艺的对准精度,制备的网栅周期误差小于6μm,边长误差小于5μm,满足实验要求.复合网栅的光学和电学性能测试结果为:加载复合网栅的蓝宝石衬底样件与未加载的相比,红外透过率曲线整体走势未发生变化,透过率整体下降了7.8%左右,与单独金属网栅相比相差3.4%,符合红外透过损失规律.该复合网栅在敏感波长为600nm光照射下测得的中心谐振频率从13.22GHz变为14.03GHz,与仿真结果基本一致,验证了光照对复合网栅电磁性能调控的可行性.     

一种采用Li3N掺杂电子注入层的底发射倒置结构OLED的制备

采用Li3N掺杂电子注入层Alq3∶Li3N,制作了一种结构为ITO/Alq3 Alq3∶Li3N/Alq3/NPB/MoO3/Al的倒置底发射有机发光器件.其中ITO玻璃作为透明阴极,金属Al作为顶部阳极,在ITO阴极与电子传输层之间加入Li3N n型掺杂层,改善了该器件的电子注入和传输能力|在Al阳极与空穴传输层之间加入MoO3缓冲层,降低了Al阳极与NPB之间较大的空穴注入势垒,改善了空穴注入能力.实验表明:此结构的倒置底发射有机发光器件性能可达到传统结构的常用有机发光器件如ITO/NPB/Alq3/LiF/Al的性能,完全可以满足非晶硅薄膜晶体管有源有机发光器件中驱动电路的匹配及性能要求.     

Short-gate AlGaN/GaN high-electron mobility transistors with BGaN buffer

Using the semi-insulating property and small lattice constant a of wurtzite BGaN alloy, we propose a BGaN buffer with a B-content of 1% to enhance two-dimensional electron gas(2 DEG) confinement in a short-gate AlGaN/GaN highelectron mobility transistor(HEMT). Based on the two-dimensional TCAD simulation, the direct current(DC) and radio frequency(RF) characteristics of the AlGaN/GaN/B_(0.01)Ga_(0.99)N structure HEMTs are theoretically studied. Our results show that the BGaN buffer device achieves good pinch-off quality and improves RF performance compared with GaN buffer device. The BGaN buffer device can allow a good immunity to shift of threshold voltage for the aspect ratio(LG/d)down to 6, which is much lower than that the GaN buffer device with L_G/d=11 can reach. Furthermore, due to a similar manner of enhancing 2 DEG confinement, the B_(0.01)Ga_(0.99)N buffer device has similar DC and RF characteristics to those the AlGaN buffer device possesses, and its ability to control short-channel effects(SCEs) is comparable to that of an Al_(0.03)Ga_(0.97)N buffer. Therefore, this BGaN buffer with very small B-content promises to be a new method to suppress SCEs in GaN HEMTs.     

Simulation study of InAlN/GaN high-electron mobility transistor with AlInN back barrier

In this work, we use a 3-nm-thick Al_(0.64)In_(0.36)N back-barrier layer in In_(0.17)Al_(0.83) N/Ga N high-electron mobility transistor(HEMT) to enhance electron confinement. Based on two-dimensional device simulations, the influences of Al_(0.64)In_(0.36) N back-barrier on the direct-current(DC) and radio-frequency(RF) characteristics of In AlN/GaN HEMT are investigated, theoretically. It is shown that an effective conduction band discontinuity of approximately 0.5 eV is created by the 3-nm-thick Al_(0.64)In_(0.36) N back-barrier and no parasitic electron channel is formed. Comparing with the conventional In AlN/GaN HEMT, the electron confinement of the back-barrier HEMT is significantly improved, which allows a good immunity to short-channel effect(SCE) for gate length decreasing down to 60 nm(9-nm top barrier). For a 70-nm gate length, the peak current gain cut-off frequency( f_T) and power gain cut-off frequency( f_(max)) of the back-barrier HEMT are172 GHz and 217 GHz, respectively, which are higher than those of the conventional HEMT with the same gate length.     

Performance of La₂O₃/InAlN/GaN metal-oxide-semiconductor high electron mobility transistors

We report on the performance of La2O3/InAlN/GaN metal-oxide-semiconductor high electron mobility transistors(MOSHEMTs) and InAlN/GaN high electron mobility transistors(HEMTs).The MOSHEMT presents a maximum drain current of 961 mA/mm at Vgs = 4 V and a maximum transconductance of 130 mS/mm compared with 710 mA/mm at Vgs = 1 V and 131 mS/mm for the HEMT device,while the gate leakage current in the reverse direction could be reduced by four orders of magnitude.Compared with the HEMT device of a similar geometry,MOSHEMT presents a large gate voltage swing and negligible current collapse.     

Performance of La2O3/InAlN/GaN metal—oxide—semiconductor high electron mobility transistors

We report on the performance of La2O3/InAlN/GaN metal-oxide-semiconductor high electron mobility transistors(MOSHEMTs) and InAlN/GaN high electron mobility transistors(HEMTs).The MOSHEMT presents a maximum drain current of 961 mA/mm at Vgs = 4 V and a maximum transconductance of 130 mS/mm compared with 710 mA/mm at Vgs = 1 V and 131 mS/mm for the HEMT device,while the gate leakage current in the reverse direction could be reduced by four orders of magnitude.Compared with the HEMT device of a similar geometry,MOSHEMT presents a large gate voltage swing and negligible current collapse.     

Enhanced performance of AlGaN-based ultraviolet light-emitting diodes with linearly graded AlGaN inserting layer in electron blocking layer

The conventional stationary Al content Al GaN electron blocking layer(EBL) in ultraviolet light-emitting diode(UV LED) is optimized by employing a linearly graded Al Ga N inserting layer which is 2.0 nm Al_(0.3) Ga_(0.7) N/5.0 nm Alx Ga_(1-x) N/8.0 nm Al_(0.3) Ga_(0.7) N with decreasing value of x. The results indicate that the internal quantum efficiency is significantly improved and the efficiency droop is mitigated by using the proposed structure. These improvements are attributed to the increase of the effective barrier height for electrons and the reduction of the effective barrier height for holes,which result in an increased hole injection efficiency and a decreased electron leakage into the p-type region. In addition,the linearly graded AlGaN inserting layer can generate more holes in EBL due to the polarization-induced hole doping and a tunneling effect probably occurs to enhance the hole transportation to the active regions, which will be beneficial to the radiative recombination.     

A simulation study of field plate termination in Ga_2O_3 Schottky barrier diodes

In this work, the field plate termination is studied for Ga_2O_3 Schottky barrier diodes(SBDs) by simulation. The influence of field plate overlap, dielectric material and thickness on the termination electric field distribution are demonstrated.It is found that the optimal thickness increases with reverse bias increasing for all the three dielectrics of SiO_2, Al_2 O_3, and HfO_2. As the thickness increases, the maximum electric field intensity decreases in SiO_2 and Al_2O_3, but increases in HfO_2.Furthermore, it is found that SiO_2 and HfO_2 are suitable for the 600 V rate Ga_2O_3 SBD, and Al_2O_3 is suitable for both600 V and 1200 V rate Ga_2O_3 SBD. In addition, the comparison of Ga_2O_3 SBDs between the SiC and GaN counterpart reveals that for Ga_2O_3, the breakdown voltage bottleneck is the dielectric. While, for SiC and GaN, the bottleneck is mainly the semiconductor itself.     

Fang–Howard wave function modelling of electron mobility in AlInGaN/AlN/InGaN/GaN double heterostructures

To study the electron transport properties in InGaN channel-based heterostructures,a revised Fang-Howard wave function is proposed by combining the effect of GaN back barrier.Various scattering mechanisms,such as dislocation impurity(DIS) scattering,polar optical phonon(POP) scattering,piezoelectric field(PE) scattering,interface roughness(IFR) scattering,deformation potential(DP) scattering,alloy disorder(ADO) scattering from InGaN channel layer,and temperature-dependent energy bandgaps are considered in the calculation model.A contrast of AlInGaN/AlN/InGaN/GaN double heterostructure(DH) to the theoretical AlInGaN/AlN/InGaN single heterostructure(SH) is made and analyzed with a full range of barrier alloy composition.The effect of channel alloy composition on InGaN channel-based DH with technologically important Al(In,Ga)N barrier is estimated and optimal indium mole fraction is 0.04 for higher mobility in DH with Al_(0.4)In_(0.07)Ga_(0.53)N barrier.Finally,the temperature-dependent two-dimensional electron gas(2 DEG) density and mobility in InGaN channel-based DH with Al_(0.83)In_(0.13)Ga_(0.0)4 N and Al_(0.4)In_(0.07)Ga_(0.53)N barrier are investigated.Our results are expected to conduce to the practical application of InGaN channel-based heterostructures.     

An improved design for Al Ga N solar-blind avalanche photodiodes with enhanced avalanche ionization

To enhance the avalanche ionization, we designed a new separate absorption and multiplication AlGaN solarblind avalanche photodiode(APD) by using a high/low-Al-content AlGaN heterostructure as the multiplication region instead of the conventional AlGaN homogeneous layer. The calculated results show that the designed APD with Al_(0.3)Ga_(0.7)N/Al_(0.45)Ga_(0.55)N heterostructure multiplication region exhibits a 60% higher gain than the conventional APD and a smaller avalanche breakdown voltage due to the use of the low-Al-content Al_(0.3)Ga_(0.7)N which has about a six times higher hole ionization coefficient than the high-Al-content Al_(0.45)Ga_(0.55)N. Meanwhile, the designed APD still remains a good solar-blind characteristic by introducing a quarter-wave AlGaN/AlN distributed Bragg reflectors structure at the bottom of the device.     

AlGaN/GaN双异质结F注入增强型高电子迁移率晶体管

理论模拟了不同GaN沟道厚度的双异质结(AlGaN/GaN/AlGaN/GaN)材料对高电子迁移率晶体管(HEMT)特性的影响,并模拟了不同F注入剂量下用该材料制作的增强型器件的特性差异.采用双异质结材料,结合F注入工艺成功地研制出了较高正向阈值电压的增强型HEMT器件.实验研究了三种GaN沟道厚度制作的增强型器件直流特性的差异,与模拟结果进行了对比验证.采用降低的F注入等离子体功率,减小了等离子体处理工艺对器件沟道迁移率的损伤,研制出的器件未经高温退火即实现了较高的跨导和饱和电流特性.对14 nm GaN沟道厚度的器件进行了阈值电压温度稳定性和栅泄漏电流的比较研究,并且分析了双异质结器件的漏致势垒降低效应.