GaN HFET偏置转换中的亚稳态能带(续)

Metastable Energy Band in GaN HFET Bias Conversion

从场效应管瞬态电流谱中慢峰展示的异质结慢充电过程出发,提出了研究GaN HFET偏置转换中出现的亚稳态新概念。利用亚稳态随时间的缓变特征,建立了自洽求解二维泊松方程和薛定谔方程的能带计算方案。选用能带峰和填充能级来描绘亚稳态,编制成计算不同应力偏置和测试偏置下亚稳态能带的计算软件。运用新编软件计算了不同能带峰和填充能级下的亚稳态能带。详细描述了偏置转换中产生的能带谷充电过程及外沟道堵塞,由此建立起应力偏置与测试偏置下动态电流间的关联。从场效应管射频工作中栅、漏电压的变化条件出发提出新的电流崩塌动态模型。运用应力偏置和测试偏置下的定态能带和亚稳态能带解释了瞬态电流谱随应力偏置和测试偏置的变化行为。最后讨论亚稳态能带在GaN HFET研究中的重要意义。

Starting from the heterojunction slow charging process exhibited by the slow peak in the transient current spectrum of FET,a new concept of metastable state in GaN HFET bias conversion is proposed.Using the gradual change characteristics of metastable state with time,an energy band calculation scheme for self-consistent solution of two-dimensional Poisson equation and Schr?dinger equation is established.The peak band and filling levels are used to characterize the metastable states,and the calculation software is compiled to calculate the metastable energy bands for different stress biases and test biases.The metastable energy bands at different energy peaks and filling levels are calculated using new software.The band-growth charging process and the outer channel blockage generated during the bias switching are described in detail.This establishes the relationship between the stress bias and the dynamic current under the test bias.A new current collapse dynamic model is proposed based on the variation conditions of gate and drain voltage in FET operation.The steady-state and metastable energy bands under different stress bias and test bias conditions are used to explain the behavior of the transient current spectrum as a function of stress bias and test bias.Finally,the significance of the metastable energy band in the research of GaN HFET is discussed.