AlGaN基共振腔增强的p-i-n型紫外探测器

设计了目标探测波长为320nm的AlGaN基共振腔增强的p-i-n型紫外光电探测器,共振腔由分别作为底镜和顶镜的AlN/Al0.3Ga0.7N布拉格反射镜和空气/GaN界面组成,有源区p-GaN/i-GaN/n-Al0.38Ga0.62N被置于腔内.该结构采用金属有机物化学气相淀积(MOCVD)方法在蓝宝石衬底和GaN模板上外延生长得到.光谱响应测试显示了正入射时该器件在波长313nm处出现响应的选择增强,零偏压下响应度为14mA/W.     

p-GaN/Al0.35Ga0.65N/GaN应变量子阱肖特基紫外探测器

报道了p-GaN/Al0.35Ga0.65N/GaN应变量子阱结构的肖特基紫外探测器的制备及性能.器件的测试结果表明,在p-GaN/Al0.35Ga0.65N/GaN双异质结中强烈的压电极化和Stark效应共同作用下使得器件在正偏和反偏时的响应光谱都向短波方向移动了10nm.零偏下器件在280nm时的峰值响应为0.022A/W,在反向偏压为1V时,峰值响应增加到0.19A/W,接近理论值.在正向偏压下器件则呈平带状态,并在283和355nm处分别出现了两个小峰.在考虑极化的情况下,通过器件中载流子浓度分布的变化解释了器件在不同偏压下的响应特性,发现p-GaN/Al0.35Ga0.65N/GaN中的极化效应对器件的响应特性影响很大,通过改变偏压和适当的优化设计可以使探测器在紫外波段进行选择性吸收.     

p-GaN/Al0.35Ga0.65N/GaN应变量子阱肖特基紫外探测器

报道了p-GaN/Al0.35Ga0.65N/GaN应变量子阱结构的肖特基紫外探测器的制备及性能.器件的测试结果表明,在p-GaN/Al0.35Ga0.65N/GaN双异质结中强烈的压电极化和Stark效应共同作用下使得器件在正偏和反偏时的响应光谱都向短波方向移动了10nm.零偏下器件在280nm时的峰值响应为0.022A/W,在反向偏压为1V时,峰值响应增加到0.19A/W,接近理论值.在正向偏压下器件则呈平带状态,并在283和355nm处分别出现了两个小峰.在考虑极化的情况下,通过器件中载流子浓度分布的变化解释了器件在不同偏压下的响应特性,发现p-GaN/Al0.35Ga0.65N/GaN中的极化效应对器件的响应特性影响很大,通过改变偏压和适当的优化设计可以使探测器在紫外波段进行选择性吸收.     

AlGaN/GaN/InGaN对称分别限制多量子阱激光器的优化设计

采用一维传递矩阵法模拟计算了AlGaN/GaN/InGaN对称分别限制多量子阱激光器(发射波长为396.6nm)的波导特性.以光限制因子、阈值电流密度和功率效率作为优化参量,获得激光器的优化结构参数为:3周期量子阱In0.02Ga0.98N/In0.15Ga0.85N(10.5nm/3.5nm)作为有源层,90nm In0.1Ga0.9N为波导层,120周期Al0.25Ga0.75N/GaN(2.5nm/2.5nm)为限制层.     

AlGaN/GaN/InGaN对称分别限制多量子阱激光器的优化设计

采用一维传递矩阵法模拟计算了AlGaN/GaN/InGaN对称分别限制多量子阱激光器(发射波长为396.6nm)的波导特性.以光限制因子、阈值电流密度和功率效率作为优化参量,获得激光器的优化结构参数为:3周期量子阱In0.02Ga0.98N/In0.15Ga0.85N(10.5nm/3.5nm)作为有源层,90nm In0.1Ga0.9N为波导层,120周期Al0.25Ga0.75N/GaN(2.5nm/2.5nm)为限制层.     

用于紫外探测器的AlGaN/GaN异质结构的Ti/Al/Ni/Au欧姆接触特性

采用Ti/Al/Ni/Au多层金属体系在Al0.27Ga0.73N/GaN异质结构上制备了欧姆接触. 分别采用线性传输线方法(LTLM)和圆形传输线方法(CTLM)对其电阻率进行了测试. 当Ti(10nm)/Al(100nm)/Ni(40nm)/Au(100nm)金属体系在650℃高纯N2气氛中退火30s时,测量得到的最小比接触电阻率为1.46E-5Ω·cm2. 并制备了Al0.27Ga0.73N/GaN光导型紫外探测器,通过测试发现探测器的暗电流-电压曲线呈线性分布. 实验结果表明在Al0.27Ga0.73N/GaN异质结构上获得了好的欧姆接触,能够满足制备高性能AlGaN/GaN紫外探测器的要求.     

用于紫外探测器的AlGaN/GaN异质结构的Ti/Al/Ni/Au欧姆接触特性

采用Ti/Al/Ni/Au多层金属体系在Al0.27Ga0.73N/GaN异质结构上制备了欧姆接触.分别采用线性传输线方法(LTLM)和圆形传输线方法(CTLM)对其电阻率进行了测试.当Ti(10nm)/Al(100nm)/Ni(40nm)/Au(100nm)金属体系在650℃高纯N2气氛中退火30s时,测量得到的最小比接触电阻率为1.46×10-5Ω·cm2.并制备了Al0.27Ga0.73N/GaN光导型紫外探测器,通过测试发现探测器的暗电流.电压曲线呈线性分布.实验结果表明在Al0.27 Ga0.73N/GaN异质结构上获得了好的欧姆接触,能够满足制备高性能AlGaN/GaN紫外探测器的要求.     

fmax为107GHz的AlGaN/GaN HFET

UCLA,JPL和Epitronics报道了在半绝缘4H-SiC衬底上生长的非掺杂沟道Al0.30Ga0.70N/GaN HFET,器件没有制作空气桥,获得的fmax达到了107GHz的新记录.该器件包括一个100nm AlN缓冲层、1.25nm的未掺杂GaN、3nm的未掺Al0.30Ga0.70N和n型重掺杂(Si=1×1019cm-3)的30nm的Al0.30Ga0.70N层.栅长为0.2μm,由于在AlGaN层中的Al含量高和n型掺杂重,获得的源漏欧姆接触电阻为0.15Ω*mm.除了优越的频率特性,该器件的跨导为260mS/mm(栅的反向偏置电压为3.5V),饱和电流密度为1.2A/mm.     

AlGaN基PIN光电探测器的模型与模拟

在漂移扩散方程的基础上建立了AlGaN p-I-n光电探测器的物理模型,分析了多种结构AlGaN p-I-n光电探测器的光谱响应,并讨论了AlGaN/GaN异质结界面极化效应对太阳盲区p-GaN/I-Al0.33Ga0.67N/n-GaN倒置异质结结构p-I-n光电探测器(inverted heterostructure photodetectors,IHPs)UV/Solar选择比(280nm与320nm响应度之比)的影响．结果表明：优化p层是提高器件光谱响应的有效途径;为获得较高的UV/Solar选择比,光伏模式(零偏压)为太阳盲区p-GaN/I-Al0.33Ga0.67N/n-GaN IHPs的最佳工作模式;在光伏模式下考虑极化效应影响时,Ga面p-GaN/I-Al0.33Ga0.67N/n-GaN IHPs器件的UV/Solar选择比可达750,与Tarsa等人报道的三个量级的实验结果基本一致．     

肖特基C-V法研究AlxGa1-xN/GaN异质结界面二维电子气

通过对Pt/AI0 22Ga078N/GaN肖特基二极管的C-V测量,研究分析了A1022Ga078N/GaN异质结界面二维电子气(2DEG)浓度及其空间分布.测量结果表明,Al0.22Ga.8N/GaN异质结界面2DEG浓度峰值对应的深度在界面以下1.3nm处,2DEG分布峰的半高宽为2.3nm,2DEG面密度为6.5×1012cm-2.与AlxGa1xAs/GaAs异质结比,其2DEG面密度要高一个数量级,而空间分布则要窄一个数量级.这主要归结于A1xGa1-xN层中～MV/cm量级的压电极化电场和自发极化电场对AlxGa1-xN/GaN异质结能带的调制和AlxGa1xN/GaN异质结界面有更大的导带不连续.     

Near ultraviolet optically pumped vertical cavity laser

Optically pumped near ultraviolet vertical cavity laser operation (VCSEL) has been obtained under quasi-continuous wave conditions at room temperature near 383 nm from shallow InGaN/GaN multiple quantum wells (MQWs). Low loss optical resonators were fabricated by using in-situ grown (Al,Ga)N distributed Bragg reflectors that featured strain engineering design for high optical morphology, in combination with low-loss dielectric multilayer mirrors     

蓝色发光GaN纳米晶和晶体的XAFS研究

利用XSAFS（X－射线吸收精细结构）方法研究六方的纳为晶和晶体GaN在78K和300K温度下Ga原子的局域配位环境结构,对于第一近邻Ga－N配位,纳米晶GaN的平均增长R、配位数N、热无序度σT和结构无序度σs与晶体GaN的相近,分别为0．194nm、4．0、0．0052nm、0．0007nm;当温度从78K增加到300K,GaN样品中Ga－N配位的σT增加不多,小于0．0005nm,表明第一近邻Ga－N配位的共价键作用力较强,几乎不受温度和晶体状态的影响。对于第二近邻Ga-Ga配位,R为0．318nm,纳米晶GaN的σs（0．0057NM）比晶体GaN的（0．001nm )大0．0047nm;在78K和300K时,纳米晶GsA样品的Ga-Ga位位的σT分别为0．0053nm和0.0085nm,这一结果表明Ga-Ga配位的σT受温度变化产生很大影响,纳米晶GaN中Ga原子的局域配位环境与晶体GaN的差别主要表现在第二近邻Ga-Ga配位的σs相对较大,可能是由于纳米晶GaN内部缺陷及存在较多的表面不饱和配位原子所致。     

Improvement in the characteristics of GaN-based light-emitting diodes by inserting AlGaN-GaN short-period superlattices in GaN underlayers

We report the influence of short-period superlattice (SPSL)-inserted structures in the underlying undoped GaN on the characteristics of GaN-based light-emitting diodes (LEDs). The measurements of current-voltage (I-V) curves indicate that GaN-based LEDs having pseudomorphic Al/sub 0.3/Ga/sub 0.7/N(2 nm)-GaN(2 nm) SPSL-inserted structures exhibit improvements in device characteristics with the best LED being inserted with two sets of five-pair Al/sub 0.3/Ga/sub 0.7/N(2 nm)-GaN(2 nm) SPSL structure. Based upon the results of etch pit counts, double-crystal X-ray diffraction measurements and transmission electron microscopic observations of the GaN-based LEDs, it was found that the Al/sub 0.3/Ga/sub 0.7/N(2 nm)-GaN(2 nm) SPSL-inserted structures tended to serve as threading dislocation filters in the LEDs so that the improved I-V characteristics were achieved.     

竹叶状GaN纳米带的制备

为了制备GAN纳米带,用射频磁控溅射法在Si(111)衬底上先溅射ZnO中间层,接着溅射Ga2O3,然后ZnO/Ga2O3膜在开管炉中1000℃下常压通氨气进行氨化。在氨气气氛中ZnO在高温下挥发,借助于ZnO挥发的帮助,Ga2O3与NH3反应自组装生成GaN纳米带。XRD分析结果表明GaN纳米带为六方纤锌矿结构,利用SEM观测GaN纳米带具有竹叶状形貌,PL谱测量发现了位于370nm处和460nm处的室温光致发光峰。     

纤锌矿GaN/AlxGa1-xN量子阱中自由极化子能级

采用Lee-Low-Pines (LLP)变分法研究了纤锌矿GaN/Al0.3Ga0.7N量子阱中自由极化子能量和电子-声子相互作用对自由极化子能量的影响.理论计算中考虑了量子阱中定域声子模(Confined phonon modes)和半空间声子模(Half-space phonon modes)的影响以及电子有效质...     

GaN从蓝宝石衬底上激光剥离技术的研究

通过激光剥离成功分离了 Ga N膜及其蓝宝石衬底。位于界面处的 Ga N吸收了波长 2 48nm的激光辐射 ,导致其热分解 ,产生 Ga和 N2 气。再将样品加热到 Ga的熔点 (2 9°C)以上 ,即可很方便地除去蓝宝石衬底。对于激光分离前后的 Ga N样品 ,进行了原子力显微镜 (AFM)和 X射线衍射实验 (XRD)的测量 ,证实了剥离过程并未改变 Ga N膜的质量。并进一步讨论了激光剥离的阈值能量密度和避免 Ga N膜破裂的几种方法。     

AlGaN/GaN-HEMTs with a breakdown voltage higher than 100 V and maximum oscillation frequency f max as high as 100 GHz

Semiconductors - The N-Al0.27Ga0.73N/GaN High Electron Mobility Transistors (HEMTs) with different gate lengths L g (ranging from 170 nm to 0.5 μm) and gate widths W s (ranging from 100 to...     

Improvement of InGaN/GaN laser diodes by using a Si-doped In/sub 0.23/Ga/sub 0.77/N/GaN short-period superlattice tunneling contact layer

InGaN/GaN multiple-quantum-well laser diode (LD) structures, including an Si-doped n/sup +/-In/sub 0.23/Ga/sub 0.77/N/GaN short-period superlattice (SPS) tunneling contact layer, are grown on c-face sapphire substrates by metalorganic vapor-phase epitaxy. The In/sub 0.23/Ga/sub 0.77/N/GaN(n/sup +/)-GaN(p) tunneling junction, which uses a low-resistivity n/sup +/-In/sub 0.23/Ga/sub 0.77/N/GaN SPS instead of a high-resistivity p-type GaN as a top contact layer, allows the reverse-biased tunnel junction to form a "quasi-ohmic" contact. Experimental results indicate that LDs with n/sup +/-In/sub 0.23/Ga/sub 0.77/N/GaN SPS contacting layers can achieve a lower threshold current and longer lasing duration under pulsed operation. Moreover, when the input pulse width is lengthened from 300 ns to 2 /spl mu/s, the lasing duration of the LD with Pt ohmic contact is three times longer than that of the LD with Ni/Au ohmic contacts. Therefore, we conclude that nitride-based LDs with an SPS reversed-tunneling contact layer may significantly reduce the contact resistance of an anode electrode and thereby increase the thermal stability of the device reliability.