增强型GaN绝缘栅HEMT线性电荷控制解析模型

基于MIS理论和含极化的泊松方程,应用费米能级与二维电子气密度线性近似,并考虑计入了绝缘体/AlGaN界面的陷阱或离子电荷,导出建立了适用于增强型且兼容耗尽型AlGaN/GaN绝缘栅HEMT的线性电荷控制解析模型。研究表明,Insulator/AlGaN界面陷阱密度在1013cm-2数量级;基于该模型的器件转移特性的理论结果与器件的实测转移特性数据比较符合。该模型可望用于器件性能评估和设计优化。     

AlN阻挡层对AlGaN/GaNHEMT器件的影响

利用低压MOCVD技术在蓝宝石衬底上生长了AlGaN/GaN异质结和AlGaN/AlN/GaN异质结二维电子气材料,采用相同器件工艺制造出了AlGaN/GaN HEMT器件和AlGaN/AlN/GaN HEMT器件.通过对两种不同器件的比较和讨论,研究了AlN阻挡层的增加对AlGaN/GaN HEMT器件性能的影响.     

GaN/AlGaN超晶格透射电镜分析

用MOCVD法生长了120周期的GaN/Al0.14Ga0.86N超晶格，激光剥离技术被有效地用于GaN/AlGaN超晶格截面透射电镜样品的制作. 用透射电子显微镜观察到了清晰的超晶格及晶胞周期结构，电子衍射也表明生长的超晶格样品质量较好. 在透射电镜图中看到了Al, Ga原子的聚居点，这些聚居点达到应力临界时将可能成为新缺陷的起点. 同时观察到GaN缓冲层中的线缺陷大多呈现弯曲的弧形，这是外延生长导致的.     

全固态高灵敏紫外探测器技术的研究进展

全固态高灵敏度的半导体紫外探测器性能优越,在多个领域有着广泛的应用需求。文章简要综述了该类技术的研究进展,并对其发展趋势进行了展望。     

Off-state breakdown and leakage current transport analysis of AlGaN/GaN high electron mobility transistors

Off-state breakdown characteristics of AlGaN/GaN high-electron-mobility transistors have been studied based on drain current injection method. It is found that at low drain current injection level, the observed premature breakdown is caused by excess gate-to-drain leakage current. Nevertheless, at high drain injection current level, buffer-leakage-dominated breakdown proceeds gate-leakage-dominated breakdown as the gate bias increases from pinch-off voltage to deep-depletion voltage. In both breakdown regions, the breakdown voltages show negative temperature coefficients. The buffer-leakage-induced breakdown should be defect-related, which is confirmed by temperature-dependent buffer leakage measurements.     

Response time improvement of AlGaN photoconductive detectors by adjusting crystal-nuclei coalescence process in metal organic vapor phase epitaxy

AlGaN photoconductive ultraviolet detectors are fabricated to study their time response characteristics. Persistent photoconductivity,a deterring factor for the detector response time,is found to be strongly related to the grain boundary density in AlGaN epilayers.By improving the crystal-nuclei coalescence process in metal organic vapor phase epitaxy,the grain-boundary density can be reduced,resulting in an-order-of-magnitude decrease in response time.     

The effects of gate length variation and trapping effects on the transient response of AlGaN/GaN HEMT’s on SiC substrates

In AlGaN/GaN heterostructure field-effect transistors, the surface defects and dislocations may serve as trapping centers and affect the device performance via leakage current. In this paper we report results of our investigation of the trapping characteristics of Al_0.25Ga_0.75N/GaN HEMT using the Conductance Deep Level Transient Spectroscopy (CDLTS). Two deep level electronic defects were observed labeled E₁ and HL₁, with activation energies E_a1 = 1.36 eV and E_a2 = 0.63 eV. The hole-trap HL₁ is characterized for the first time in our studies. We identified the characteristics of the traps at the AlGaN/GaN interface adjoining the channel and the surface along the ungated region between the gate and the drain, as well as the effects of the surface traps.     

最大振荡频率为200 GHz的蓝宝石衬底AlGaN/GaN HEMT

本文报道了fmax为200GHz的基于蓝宝石衬底的AlGaN/GaN 高电子迁移率晶体管（HEMT）。外延材料结构采用了InGaN背势垒层来减小短沟道效应,器件采用了凹栅槽和T型栅结合的工艺,实现了Ka波段AlGaN/GaN HEMT。器件饱和电流达到1.1A/mm,跨导为421mS/mm,截止频率（fT）为30GHz,最大振荡频率（fmax）为105GHz。采用了湿法腐蚀工艺将器件的Si3N4钝化层去除后,器件的Cgs和Cgd减小,器件截止频率提高到50GHz,最大振荡频率提高到200GHz。     

Optical properties of undoped n-AlGaN/GaN superlattices as affected by built-in and external-electric field and by ar-implantation-induced partial disordering

High-resolution x-ray diffraction patterns and 90 K microcathodoluminescence (MCL) spectra were taken for undoped, symmetric AlGaN/GaN superlattices (SLs) with GaN quantum-well (QW) widths of 35 Å and 80 Å. The short-period SL spectra were blue shifted by about 60 meV compared to the GaN substrate, and the magnitude of the blue shift was increased by about 20 meV by application of a reverse bias of ?3 V (electric field of about 4 · 10⁵ V/cm) to a Schottky diode prepared on this SL. A small red shift of about 40 meV compared to GaN was observed for the long-period SL. The two latter observations were interpreted as manifestations of the presence of a strong built-in piezoelectric field, giving rise to the quantum-confined Stark effect (QCSE). Partial disordering of the short-period SL was observed after Ar ion implantation (energy 150 keV, dose 8·10¹³ cm^?2 and 80 keV, 2·10¹³ cm^?2) and subsequent annealing at 1000°C for 3 h under the protective layer of Si₃N₄. However, it was observed that this partial disordering was accompanied by strain relaxation via formation of misfit dislocations or cracks.     

Influence of dual-frequency plasma-enhanced chemical-vapor deposition Si<Subscript>3</Subscript>N<Subscript>4</Subscript> passivation on the electrical characteristics of AlGaN/GaN heterostructure field-effect transistors

The influence of dielectric stress on the direct current (DC) electrical characteristics of AlGaN/GaN heterostructure field-effect transistors (HFETs) has been investigated. Dual-frequency plasma deposition was used to vary the amount of stress induced by a passivating dielectric on the surface of the devices. Initial data suggested a strong influence from the induced dielectric stress, but the low-frequency, radio-frequency (RF) excitation of the plasma deposition process was found to induce a severe nonreversible damage to the exposed AlGaN surface through N ion bombardment. The consequence is a drastic reduction of the sheet carrier concentration and mobility of the two-dimensional electron gas (2DEG). Subsequently, an alternative damage-free technique using a helium precursor was used to obtain compressive films. Based on the results, uniform dielectric stress has a minimal impact on the polarization charges within the AlGaN barrier.