GaN基三维结构生长与器件应用

目前,c面氮化镓(GaN)基发光二极管的制备技术已经十分成熟并取得了商业化成功,但仍面临极化电场导致的大电流密度下效率下降(Droop效应)和黄绿光波段效率低的问题.为消除极化电场的影响,人们开始关注半极性和非极性面GaN.其中,基于传统极性面衬底通过三维结构生长来获得半极性和非极性GaN的方法,由于其低成本和生长的灵活性,受到了广泛研究.本文首先总结了三种GaN三维结构的制备方法并分析其生长机理.接着,在此基础上介绍了不同晶面InGaN量子阱的外延生长和发光特性.最后,列举了GaN基三维结构在半极性面LED、颜色可调LED和无荧光粉白光发光二极管方面的应用.     

基于X射线衍射的GaN薄膜厚度的精确测量

结合Williamson-Hall plot方法和线型分析方法的优点，提出了一种有效分离有限晶粒尺寸和非均匀应力等X射线衍射展宽效应的方法，可以用于GaN外延层厚度等参数的快速精确测量.用该方法对一系列在蓝宝石衬底上生长的厚度在0.7—4.2μm的GaN外延膜进行了测量，并与椭圆偏振光谱法测量结果进行了比较，结果表明其差别<4%，反应了这种方法的准确性. 关键词： GaN薄膜 厚度测量 X射线衍射     

非故意掺杂GaN薄膜方块电阻与载气中N2比例关系研究

利用金属有机气相外延方法研究了非故意掺杂GaN薄膜的方块电阻与高温GaN体材料生长时载气中N₂比例的关系.研究发现，随着载气中N₂比例的增加，GaN薄膜方块电阻急剧增加.当载气中N₂比例为50%时，GaN薄膜方块电阻达1.1×10⁸Ω/□，且GaN表面平整，均方根粗糙度为0.233nm.二次离子质谱分析发现，载气中N₂比例不同的样品中碳、氧杂质含量无明显差别.随着载气中N₂比 关键词： 半绝缘GaN薄膜 载气 金属有机气相外延 位错     

Vertical and Smooth, etching of InP by Cl2／CH4／Ar Inductively Coupled Plasma at Room Temperature

We study the room-temperature dry, etching of InP by inductively coupled plasma (ICP) using C12/CH4/Ar mixtures. Etches were characterized in terms of anisotropy and surface roughness by scanning electron microscopy and atomic force microscopy, respectively. It is found that the flow ratio between C12 and Ctt4, ICP power, rf chuck power, and table temperature can greatly influence the, etching results. By adjusting, etching parameters,vertical sidewall and smooth surface can be obtained simultaneously, together with a moderate, etch rate and a good select ratio. The root-mean-square surface roughness is measured to be as low as 0.27nm. To the best of our knowledge, this is the best result for InP to date. The, etch rate is 855nm/min, and the selectivity ratio overSi02 is estimated to be higher than 15:1. The stoichiometry of the, etched surface has also been investigated by Auger electron spectroscopy. The, etched surface is found to manifest a slight P deficiency, and the ratio between P and In reaches the stoichiometric value within about 0.75nm depth into the surface.     

Deep InP Gratings for Opto-Electronic Devices Etched by C12/CH4/Ar Inductively Coupled Plasma

Deep InP gratings are etched by C12/CH4/Ar inductively coupled plasma （ICP） at room temperature. A comparison is made between SiNz mask patterns formed by wet and dry etching. SF6 reactive ion etching is adopted for smooth and vertical sidewall. The etching conditions of C12/CH4/Ar ICP are optimized for high anisotropy, and a 1.7-μm-deep InP grating with an aspect ratio of 10：1 is demonstrated. The technique is then used for the fabrication of 1.55-μm laterally coupled distributed feedback A1GMnAs-InP laser.     

圆扫描变像管人卫激光测距技术研究

在本文中,我们设计并研制了用于毫米级精度人卫激光测距的圆扫描时间分析系统。研制的圆扫描变像管理论时间分辨率可优于3ps,可用于双色测距;偏转灵敏度高达10cm/kV,偏转空间分辨率优于24lp/mm;利用双MCP内增强,增益～1×10⁶,并有门控功能以进一步提高信噪比和动态范围。扫描控制电路能提供300MHz、10W的正弦信号,其频率、幅度、相位稳定度均可满足要求。调试过程中较好地解决了阻抗变换、空间干扰和相位正交等关键问题。在仅2W的RF功率驱动下,即可实现稳定的φ24mm的圆扫描,系统实测时间分辨率达4.8ps。在实验室实测测距精度达亚毫米级。动态实验及模拟测距表明,该时间分析系统可满足第四代人卫激光测距系统的需要。     

Investigation of External Optical Feedback Resistance of IC—DFB and GC—DFB Lasers Using a Very Simple Experimental set—up

We study the external optical feedback resistance of both index-coupled(IC) and gain-coupled distributed feed-back(DFB) lasers using a very simple experimental set-up.Though IC-DFB lasers with large coupling coefficients are found to be less sensitive to external reflection,they suffer from mode instability at high injection level.On the other hand ,the introduction of gain-coupling mechanism can significantly improve both the immunity of external optical feedback and the single mode yield of the device.     

两种不同并行敷设热力影响对比研究

油气管道敷设中存在两种并行敷设方式,输油管道并行敷设和油气管道并行敷设.受焦耳汤姆逊效应和管径差别等因素的影响,油气管道并行敷设与两条输油管道并行敷设热力影响情况有所不同.本文采用有限差分法和有限容积法相结合的数值计算方法研究了这两种不同并行敷设热力影响的区别.     

非故意掺杂GaN薄膜方块电阻与载气中N2比例关系研究

利用金属有机气相外延方法研究了非故意掺杂GaN薄膜的方块电阻与高温GaN体材料生长时载气中N2比例的关系.研究发现,随着载气中N2比例的增加,GaN薄膜方块电阻急剧增加.当载气中N2比例为50%时,GaN薄膜方块电阻达1.1×108Ω/□,且GaN表面平整,均方根粗糙度为0.233 nm.二次离子质谱分析发现,载气中N2比例不同的样品中碳、氧杂质含量无明显差别.随着载气中N2比例的增加,GaN材料中螺型位错相关缺陷密度无明显变化,而刃型位错相关缺陷密度明显增加.结果表明,刃型位错的受主补偿作用是导致GaN薄膜方块电阻变化的主要原因.