AlGaN/GaN HFET的2DEG和电流崩塌研究(Ⅰ)

Study on 2DEG and Current Collapse of AlGaN/GaN HFET

从不同的视角回顾和研究了AlGaN/GaN HFET的二维电子气(2DEG)和电流崩塌问题。阐述了非掺杂的AlGaN/GaN异质结界面存在2DEG的原动力是极化效应,电子来源是AlGaN上的施主表面态。2DEG浓度与AlGaN/GaN界面导带不连续性、AlGaN层厚和Al组分有密切关系。揭示了AlGaN/GaN HFET的2DEG电荷涨落受控于表面、界面和缓冲层中的各种缺陷及外加应力,表面空穴陷阱形成的虚栅对输入信号有旁路和延迟作用,它们导致高频及微波状态下的电流崩塌。指出由于构成电流崩塌因素的复杂性,各种不同的抑制电流崩塌方法都存在不足,因此实现该器件大功率密度和高可靠性还有很长的路要走。

The development about 2 dimensional electron gas （2DEG） and current collapse of AlGaN/ GaN HFET are reviewed and investigated from different aspects. 2DEG exists in the interface of nominally undoped heterojunction AlGaN/GaN, the polarization effect introduced 2DEG in the interface of AIGaN/GaN heterojunction, but electronical sources are from surface donor states on AlGaN. The density of 2DEG is closely affected by the conduction band offset at the AlGaN/GaN interface, the thickness of AlGaN layer and the AI mole fraction in it. Dispersion effects of 2DEG in AlGaN/GaN HFET are under the control of multifarious defects and impurity on the surface and in the material, adscititious strain or electricity. The surface hole-trapping comes into being the virtual gate, signal input are passed-by partially and delayed by it. Because of the reasons, current collapse takes place in AlGaN/GaN HFET at high frequency or microwave power. As a result of the complexity of inducing current collapse, manifold know-how is imperfection for suppressing it. So high power and high reliability AlGaN/GaN HFET is not accomplished a purpose before long.