高质量氧化镓单晶及肖特基二极管的制备

本文采用导模法生长技术,成功制备了高质量掺Si氧化镓(β-Ga₂O₃)单晶,掺杂浓度为2×10¹⁸ cm^-3.晶体呈现淡蓝色,通过劳厄衍射、阴极荧光(CL)及拉曼测试对晶体的基本性质进行了表征,结果表明晶体质量良好.紫外透过光谱证明该晶体的禁带宽度约为4.71 eV.此外,在剥离衬底上,采用电子束蒸发、光刻和显影技术制备了垂直结构的肖特基二极管,平均击穿场强EAva为2.1 MV/cm,导通电阻3 mΩ·cm²,展示了优异性能.     

In-situ SiN combined with etch-stop barrier structure for high-frequency AlGaN/GaN HEMT

The etch-stop structure including the in-situ SiN and AlGaN/GaN barrier is proposed for high frequency applications.The etch-stop process is realized by placing an in-situ SiN layer on the top of the thin AlGaN barrier.F-based etching can be self-terminated after removing SiN,leaving the AlGaN barrier in the gate region.With this in-situ SiN and thin barrier etch-stop structure,the short channel effect can be suppressed,meanwhile achieving highly precisely controlled and low damage etching process.The device shows a maximum drain current of 1022 mA/mm,a peak transconductance of 459 mS/mm,and a maximum oscillation frequency(fmax)of 248 GHz.     

露水草植物中蜕皮激素的分离和鉴定

露水草含有两种对昆虫具有蜕皮活性的物质.经物理化学分析证明是β-蜕皮激素及其2-乙酸酯.其含量为全草干重的1. 2%,地下部分干重的2. 9%.     

GaN FP-HEMTs中击穿电压与电流崩塌的关系

研究了钝化在抑制电流崩塌的同时，会引起HEMT器件击穿电压的下降.而采用场板结构的AlGaN/GaN场板HEMT器件(FP-HEMT)的击穿电压从46V提高到了148V，表明了场板对提高击穿电压有显著作用(3倍以上).接着，比较了FP-HEMT器件与常规HEMT器件，钝化后HEMT器件在应力前后的电流崩塌程度，得出了采用场板结构比之钝化对器件抑制电流崩塌有更明显作用的结论.从理论上和实验上都表明，采用场板结构能够很好解决提高击穿电压与抑制电流崩塌之间的矛盾. 关键词： GaN 场板 击穿电压 电流崩塌     

MOCVD制备InxGa1－xN/GaN MQWs的温度依赖性

利用方势阱模型对In_xGa_1－xN/GaN MQWs结构的光特性进行了量子力学定性理论分析.并在MO源流量恒定条件下，在570℃～640℃范围内进行了不同生长温度的多量子阱制备实验，对In_xGa_1－xN制备过程中的In组份掺入效率的温度依赖关系进行研究.通过对制备样品的PL谱测量分析，得到了587℃～600℃的In组份最佳掺入温度区间.     

GaN MOS-HEMT Using Ultra-Thin A1203 Dielectric Grown by Atomic Layer Deposition

We report a GaN metal-oxide-semiconductor high electron mobility transistor （MOS-HEMT） with atomic layer deposited （ALD） Al2O3 gate dielectric. Based on the previous work [Appl. Phys. Lett. 86 （2005） 063501] of Ye et al. by decreasing the thickness of the gate oxide to 3.5nm and optimizing the device fabrication process, the device with maximum transconductance of 150mS/mm is produced and discussed in comparison with the result of lOOmS/mm of Ye et al. The corresponding drain current density in the 0.8-μm-gate-length MOS-HEMT is 800mA/mm at the gate bias of 3.0 V. The gate leakage is two orders of magnitude lower than that of the conventional A1GaN/GaN HEMT. The excellent characteristics of this novel MOS-HEMT device structure with ALD Al2O3 gate dielectric are presented.     

The Anomalous Effect of Interface Traps on Generation Current in Lightly Doped Drain nMOSFET＇s

The anomalous phenomenon of generation current ICD in the lightly doped drain （LDD） nMOSFET measured under the drain bias VD-step mode is reported. We propose an assumption of activated （A） and frozen （F） traps for the VD-step mode： The A traps contributes to ICD while the F process can make them lose the roles as generation centers. The A and F regions can form the F-A region. The comparison of the F and A regions decides the role of the F-A region. The experiments confirm the assumption.     

Photoluminescence characteristics of GaN：Si

Both the electrical and optical properties are studied of the GaN：Si films with carrier concentrations ranging from 10^17cm^-3 to 10^19cm^-3.rhe results indicate that the increase in slope of carrier concentration starts to slow down when the flow rate of SiH4 is larger than 6.38μmol/min, which is attributed to the amphoteric character of Si. At the same time, the photoluminescence results show that the FWHM of UV is widened,which can be interpreted quantitatively with a semi-classic model. Furthermore, the intensity ratio between the yellow and the UV luminescences reduces monotonically with Si dopants increasing.