蓝宝石衬底上单晶InN外延膜的RF-MBE生长

采用低温氮化铟(InN)缓冲层,利用射频等离子体辅助分子束外延(RF-MBE)方法在蓝宝石衬底上获得了晶体质量较好的单晶InN外延膜.用光学显微镜观察所外延的InN单晶薄膜,表面无铟滴.InN(0002)双晶X射线衍射摇摆曲线的半高宽为14′;用原子力显微镜测得的表面平均粗糙度为3.3nm;Hall测量表明InN外延膜的室温背景电子浓度为3.3×1018cm-3,相应的电子迁移率为262cm2/(V·s).     

Investigation of the current collapse induced in InGaN back barrier AIGaN/GaN high electron mobility transistors

Current collapses were studied, which were observed in A1GaN/GaN high electron mobility transistors （HEMTs） with and without InGaN back barrier （BB） as a result of short-term bias stress. More serious drain current collapses were observed in InGaN BB A1GaN/GaN HEMTs compared with the traditional HEMTs. The results indicate that the defects and surface states induced by the InGaN BB layer may enhance the current collapse. The surface states may be the primary mechanism of the origination of current collapse in A1GaN/GaN HEMTs for short-term direct current stress.     

p-a-SiC:H/i-a-Si:H/n-μc-Si 太阳能电池效率的理论研究

用软件AMPS研究了一种新型结构的太阳能电池,通过研究界面复合速率,p型层厚度,本征层厚度,n型层厚度和掺杂浓度的变化对转换效率的影响。结果表明：用a-SiC:H 作为 p-a-SiC:H/i-a-Si:H/n-μc-Si电池的窗口层在理论上可行,并且性能更优。这一结果为非晶硅电池效率的提高提供了新思路。     

AlGaN/GaN背对背肖特基二极管氢气传感器

通过溅射的方法制作了Pt/AlGaN/GaN背对背肖特基二极管并测试了该器件对氢气的响应.研究了Pt/AlGaN/GaN背对背肖特基二极管在25和100℃时对于10%H2(N2气中)的响应,计算了器件的灵敏度;并比较了两种温度条件下器件对于氢气响应的快慢;空气中的氧气对于器件电流的恢复有重要的作用;最后由热电子发射公式计算了器件在通入10%的氢气前后有效势垒高度的变化.     

T-ZnOw高分子复合材料逾渗行为的模拟与研究

从T-ZnOw独特的空间结构出发,建立了T-ZnOw高分子复合材料的新型三维点阵模型,利用Monte Carlo方法对该系统的逾渗导通行为进行了模拟,得到点阵逾渗阈值为23.2%.结合实际计算获得了T-ZnOw的临界掺入比例,与文献报道的结果基本吻合.计算表明临界掺入比例主要取决于T-ZnOw的长径比,并与晶须尺寸以及复合材料制备工艺有关     

蓝宝石衬底上单晶InN薄膜的MOCVD生长

采用非掺GaN为缓冲层,利用金属有机物气相沉积(MOCVD)方法在蓝宝石衬底上获得了晶体质量较好的InN单晶薄膜.用光学显微镜观察得到的InN薄膜,表面无铟滴生成.INN(0002)X射线双晶衍射摇摆曲线的半峰宽为9.18;原子力显微镜测得的表面平均粗糙度为18.618nm;Hall测量得到的InN薄膜的室温背景电子浓度为1.08×1019cm-3,相应的迁移率为696cm2/(V·s).     

高阻GaN薄膜电阻率测量

建立了绝缘电阻大于1013Ω和温度起伏小于0.1℃的高阻GaN薄膜电阻率装置,并简述了其测量电阻率的原理.研究了环境温度、湿度、漏电流、数据读取时间、测量电压、样品尺寸等因素对电阻率与迁移率的影响,并讨论了各种因素所引起的测量误差.     

MOCVD方法制备高Al组分AlGaN

利用金属有机物化学气相沉积(MOCVD)技术在蓝宝石衬底上外延生长了高Al组分的AlGaN薄膜.采用透射谱的方法确定AlGaN外延层的带隙,采用X光双晶衍射(DCXRD)的ω扫描摇摆曲线表征AlGaN外延层晶体质量,采用扫描电子显微镜表征AlGaN外延层的表面形貌.对生长压力为1.33×104和0.66×104Pa的两个样品的光学性质、晶体质量及表面形貌进行了对比.     

MOCVD方法制备高Al组分AlGaN

利用金属有机物化学气相沉积(MOCVD)技术在蓝宝石衬底上外延生长了高Al组分的AlGaN薄膜.采用透射谱的方法确定AlGaN外延层的带隙,采用X光双晶衍射(DCXRD)的ω扫描摇摆曲线表征AlGaN外延层晶体质量,采用扫描电子显微镜表征AlGaN外延层的表面形貌.对生长压力为1.33×104和0.66×104Pa的两个样品的光学性质、晶体质量及表面形貌进行了对比.     

Simulation of electrical properties of InxAl1-xN/AlN/GaN high electron mobility transistor structure

Electrical properties of In_x Al_1-xN/AlN/GaN structure are investigated by solving coupled Schr（o|¨）dinger and Poisson equations self-consistently.The variations in internal polarizations in In_xAl_1-xN with indium contents are studied and the total polarization is zero when the indium content is 0.41.Our calculations show that the twodimensional electron gas（2DEG） sheet density will decrease with increasing indium content.There is a critical thickness for AIN.The 2DEG sheet density will increase with In_xAl_1-xN thickness when the AIN thickness is less than the critical value.However,once the AIN thickness becomes greater than the critical value,the 2DEG sheet density will decrease with increasing barrier thickness.The critical value of AIN is 2.8 nm for the lattice-matched In_0.18Al_0.82N/AlN/GaN structure.Our calculations also show that the critical value decreases with increasing indium content.