Large-scale SiO2 photonic crystal for high efficiency GaN LEDs by nanospherical-lens lithography

Wafer-scale SiO2 photonic crystal （PhC） patterns （SiO2 air-hole PhC, SiO2-pillar PhC） on indium tin oxide （ITO） layer of GaN-based light-emitting diode （LED） are fabricated via novel nanospherical-lens lithography. Nanoscale polystyrene spheres are self-assembled into a hexagonal closed-packed monolayer array acting as convex lens for expo- sure using conventional lithography instrument. The light output power is enhanced by as great as 40.5% and 61% over those of as-grown LEDs, for SiO2-hole PhC and SiO2-pillar PhC LEDs, respectively. No degradation to LED electrical properties is found due to the fact that SiO2 PhC structures are fabricated on ITO current spreading electrode. For SiO2- pillar PhC LEDs, which have the largest light output power in all LEDs, no dry etching, which would introduce etching damage, was involved. Our method is demonstrated to be a simple, low cost, and high-yield technique for fabricating the PhC LEDs. Furthermore, the finite difference time domain simulation is also performed to further reveal the emission characteristics of LEDs with PhC structures.     

InP基HEMT器件中二维电子气浓度及分布与沟道层厚度关系的理论分析

利用数值计算的方法研究了InP基高电子迁移率晶体管(HEMT)中沟道厚度对沟道中二维电子气(2DEG)性质的影响，并对产生这种影响的原因进行了深入探讨.计算结果表明，当沟道层厚度从10nm增加到40nm时，沟道中2DEG的密度几乎没有变化，但激发态和基态上的电子密度之比(R)先增加后减小.当沟道层厚度在20—25nm之间时，R达到最大.此结果可作为优化器件结构设计的依据. 关键词： HEMT 异质结 二维电子气 自洽计算     

Self-consistent analysis of double-δ-doped InAlAs/InGaAs/InP HEMTs

We have carried out a theoretical study of double-5-doped InAlAs/InGaAs/InP high electron mobility transistor （HEMT） by means of the finite differential method. The electronic states in the quantum well of the HEMT are calculated self-consistently. Instead of boundary conditions, initial conditions are used to solve the Poisson equation. The concentration of two-dimensional electron gas （2DEG） and its distribution in the HEMT have been obtained. By changing the doping density of upper and lower impurity layers we find that the 2DEG concentration confined in the channel is greatly affected by these two doping layers. But the electrons depleted by the Schottky contact are hardly affected by the lower impurity layer. It is only related to the doping density of upper impurity layer. This means that we can deal with the doping concentrations of the two impurity layers and optimize them separately. Considering the sheet concentration and the mobility of the electrons in the channel, the optimized doping densities are found to be 5 × 10^12 and 3× 10^12 cm^-2 for the upper and lower impurity layers, respectively, in the double-5-doped InAlAs/InGaAs/InP HEMTs.     

MBE生长InAs薄膜输运性质的研究

在ＧａＡｓ衬底上ＭＢＥ生长大失配ＩｎＡｓ薄膜，虽然在界面处存在大量位错，但仍能在ＩｎＡｓ薄膜中得到较高的电子迁移率．掺Ｓｉ样品的迁移率比同厚度未掺杂的样品要高．且对未掺杂的ＩｎＡｓ薄膜，迁移率在室温附近有一个明显的极小值．这些反常行为可以通过体层和界面层电子的并联电导模型来解释．     

硅基微电子新材料SGOI薄膜研究进展

绝缘体上的锗硅技术(SiGe on Insulator,SGOI)和以它为衬底开发的应变硅技术(Strained Silicon on Insulator,sSOI)融合了SiGe技术和SOI技术二者的优点,是近年来人们广泛重视的研究热点和硅基集成电路产业进一步发展的重要研究方向,是国际半导体技术发展路线图(ITRS)中CMOS技术今后几年发展的方向.文章综述了SGOI薄膜的多种制备方法和最新研究进展.     

水平冷壁CVD生长4H-SiC同质外延膜

采用自行设计的水平冷壁低压化学气相沉积(LPCVD)方法在偏向〈1120〉晶向8°的n型4H-SiC(0001)衬底上进行了同质外延生长.在5.3×103Pa的低压下,外延膜生长速率超过3μm/h.电容-电压法测试表明在非有意掺杂外延膜中净施主浓度为8.4×10 15cm-3.Nomarski显微镜观察表明厚外延膜的表面光滑,生长缺陷密度很低.AFM测试显示表面均方根粗糙度为0.3nm,没有观察到宏观台阶结构.Raman谱线清晰锐利,表现出典型的4H-SiC特征.在低温PL谱中,近带边区域出现很强的自由激子峰,表明样品是高质量的.     

匹配In_(0.53)Ga_(0.47)As/InP量子阱材料的GSMBE生长及特性分析

在国产CBE设备上，用GSMBE方法首次在国内成功地生长出了具有不同阱宽（1～18nm）的高质量的In0.53Ga0.47As／InP匹配量子阱结构材料，低温光致发光谱测试结果表明：量子阱材料发光谱峰强且锐，每个阱的激子跃迁峰清晰可辨．当阱宽大于6nm时，阱中激子跃迁能量的实验值与理论计算值符合得很好；当阱宽小于6nm时，实验值小于理论值；对阱宽相同的窄阱而言，我们样品的实验值高于Tsang的实验值，当阱宽小于4nm时，阱中激子跃迁谱峰的半高宽小于当量子阱界面起伏一个分子单层时所引起的展宽值，表明量子阱的界面具有原子级的平整度；与1nm阱相应的低温光致     

偏晶向(0001)Si-面衬底上4H-SiC的LPCVD外延生长

化学气相沉积（CVD）是微电子器件用SiC外延材料的主要生长技术. 为了获得高质量的4H-SiC外延材料，在偏向〈1120〉方向8. 的4H-SiC (0001) Si-面衬底上，利用台阶控制生长技术进行4H-SiC的同质外延生长. 表面形貌是SiC外延材料质量好坏的一个重要参数，为此研究了表面形貌与工艺参数的关系，探讨了4H-SiC外延膜的表面缺陷形成原因. 利用Raman散射技术研究了非均匀4H-SiC外延材料的多晶型现象.     

Ⅴ/Ⅲ比和生长温度对RF-MBE InN表面形貌的影响

由于生长InN所需平衡氮气压较高,而且InN分解温度比较低,因此在生长InN时In原子很容易在表面聚集形成In滴,使InN外延膜的表面形貌变差,影响InN外延膜质量的提高.通过研究Ⅴ/Ⅲ比和生长温度对RFMBE生长InN外延膜表面形貌的影响,发现Ⅴ/Ⅲ比和生长温度对InN外延膜表面In滴的量有重要影响.通过选择合适的Ⅴ/Ⅲ比和生长温度,得到了表面平整光亮、无In滴的InN外延膜.     

大功率氮化镓基LED关键技术研究

对大功率氮化镓基LED的关键技术，尤其是大芯片LED的结构设计，p电极的选择与制备，提取效率的提高以及倒装焊技术做了重点的介绍与讨论.