InAs量子点的原子力显微镜测试结果分析

我们利用分子束外延（ＭＢＥ）技术在ＧａＡｓ（００１）衬底上生长１８个原子层的ＩｎＡｓ,形成了纳米尺寸的ＩｎＡｓ量子点．对ＩｎＡｓ量子点进行原子力显微镜（ＡＦＭ）测量,得到了量子点的高度和横向尺寸的统计分布以及量子点的测量形貌特征．并且对测量结果利用简单的模型进行了误差的分析     

产生超短脉冲的光泵浦垂直外腔面发射激光器的研究进展

光泵浦半导体垂直外腔面发射激光器（OPS-WCSEL）在产生超短脉冲方面显示了优越的特性,在脉冲宽度、平均输出功率和脉冲重复频率等方面都得到了与传统超短脉冲激光器可比的结果．显出巨大的发展潜力。本文综合分析了用于产生超短脉冲的OPS-VECSE的基本原理和最趣研究进展,并探讨了该领域的发展方向和应用前景。     

Determination of the series resistance under the Schottky contacts of AlGaN/AlN/GaN Schottky barrier diodes

Rectangular AlGaN/AlN/GaN heterostructure field-effect transistors (HFETs) were fabricated, and the gate and the source of the HFETs consisted of AlGaN/AlN/GaN Schottky barrier diodes (SBDs). Based on the measured forward current-voltage and the capacitance-voltage characteristics of the AlGaN/AlN/GaN SBDs, the series resistance under the Schottky contacts (R_S) was calculated using the method of power consumption, which has been proved to be valid. Finally, the method of power consumption for calculating R_S was successfully used to study the two-dimensional electron gas electron mobility for a series of circular AlGaN/AlN/GaN SBDs. It is shown that the series resistance under the Schottky contacts cannot be neglected and is important for analysing and characterizing the AlGaN/AlN/GaN SBDs and the AlGaN/AlN/GaN HFETs.     

Effect of CO on Characteristics of AlGaN/GaN Schottky Diode

Pt Schottky diode gas sensors for CO are fabricated using A1GaN/GaN high electron mobility transistor（HEMTs）structure. The diodes show a remarkable sensor signal （3 mA, in N2, 2mA in air ambient） biased 2 V after 1% CO is introduced at 50℃. The Schottky barrier heights decrease for 36meV and 27meV in the two cases respectively. The devices exhibit a slow recovery characteristic in air ambient but almost none in the background of pure N2, which reveals that oxygen molecules could accelerate the desorption of CO and offer restrictions to CO detection.     

银纳米阵列直径对SERS增强效果的影响

采用电化学沉积法分别在不同孔径的阳极氧化铝(AAO)模板上沉积一系列直径不同,排列规则的银纳米阵列。以对氨基苯甲酸(PABA)和三聚氰胺两种分子分别作为探针分子, 研究了银纳米阵列的直径大小对其表面增强拉曼散射(SERS)效果的影响。结果表明, 在波长为514.5 nm的激光激发下, 探针分子的SERS信号强度随银纳米阵列直径的改变而明显变化, 并在银纳米阵列直径约为53 nm时, SERS强度达到最大。利用电磁增强机制对此实验结果进行了分析和解释。     

InGaN/GaN multiple quantum well solar cells with an enhanced open-circuit voltage

In this paper,InGaN/GaN multiple quantum well solar cells (MQWSCs) with an In content of 0.15 are fabricated and studied.The short-circuit density,fill factor and open-circuit voltage (V oc) of the device are 0.7 mA/cm 2,0.40 and 2.22 V,respectively.The results exhibit a significant enhancement of V oc compared with those of InGaN-based hetero and homojunction cells.This enhancement indicates that the InGaN/GaN MQWSC offers an effective way for increasing V oc of an In-rich In x Ga 1 x N solar cell.The device exhibits an external quantum efficiency (EQE) of 36% (7%) at 388 nm (430 nm).The photovoltaic performance of the device can be improved by optimizing the structure of the InGaN/GaN multiple quantum well.     

Broadband tunable external cavity laser using a bent-waveguide quantum-dot superluminescent diode as gain device

A broadband tunable grating-coupled external cavity laser is realized by employing a self-assembled InAs/GaAs quantum-dot (QD) superluminescent diode (SLD) as the gain device. The SLD device is processed with a bent-waveguide structure and facet antireflection (AR) coating. Tuning bandwidths of 106 nm and 117 nm are achieved under 3-A and 3.5-A injection currents, respectively. The large tuning range originates essentially from the broad gain spectrum of self-assembled QDs. The bent waveguide structure combined with the facet AR coating plays a role in suppressing the inner-cavity lasing under a large injection current.     

Influence of Ni Schottky contact thickness on two-dimensional electron-gas sheet carrier concentration of strained Al_(0.3)Ga_(0.7)N/GaN heterostructures

Ni/Au Schottky contacts with thicknesses of either 50(?)/50(?) or 600(?)/2000(?) were deposited on strained Al_(0.3)Ga_(0.7)N/GaN heterostructures.Using the measured C-V curves and I-V characteristics at room temperature,the calculated density of the two-dimensional electron-gas(2DEG) of the 600(?)/2000(?) thick Ni/Au Schottky contact is about 9.13×10~(12) cm~(-2) and that of the 50(?)/50(?) thick Ni/Au Schottky contact is only about 4.77×10~(12) cm~(-2).The saturated current increases from 60.88 to 86.3...     

GaAs/AlGaAs量子级联激光器自脉动动力学

利用步进扫描时间分辨傅里叶变换红外光谱,研究了波长9.76μm GaAs/AlGaAs量子级联激光器的准连续波激射谱.在驱动电流周期内,时间上堆叠的发射谱能够观察到明显的光强自脉动现象.有源区中的自加热积累大大影响了电子的驰豫和输运性质.热引起的在注入区较高子能级中占据的载流子由于这些子能级与下一注入区的连续态形成共振条件而泄露,而耦合阱有源区中第四子能级的存在加快了这个过程.周期性破坏和恢复的共振条件所引起的载流子泄露在很大程度上导致了时域堆叠光谱的自脉动.     

大功率In(Ga)As/GaAs量子点激光器

利用分子束外延技术和S-K生长模式,系统研究了InAs/GaAs材料体系应变自组装量子点的形成和演化.研制出激射波长λ≈960nm,条宽100μm,腔长800μm的In(Ga)As/GaAs量子点激光器:室温连续输出功率大于3.5W,室温阈值电流密度218A/cm2,0.61W室温连续工作寿命超过3760小时.