GaN异质结场效应管中栅、漏电压对电子气的控制(续)

Control of Gate and Drain Voltage on Electron Gas in GaN Heterojunction Field Effect Transistor

从自洽求解二维泊松方程和薛定谔方程出发,编制出计算GaN HFET内不同栅、漏电压下沟道能带、电子气密度及量子电容的软件,研究场效应管的电荷控制和DIBL。在异质结沟道阱研究中,改变栅电压算出的电子气密度及量子电容同C-V实验测试结果相吻合,证明求解薛定谔方程是研究异质结场效应管电荷控制的有效方法。考虑外沟道渗透到内沟道的电场梯度以后,算出了场效应管的电子气密度及量子电容。场效应管模拟算得的量子电容同实验测得的栅-源和栅-漏电容相吻合。研究了不同栅、漏电压和电场梯度渗透下的内沟道能带,发现漏电压引起的电场梯度渗透使内沟道能带下弯,导致阈值电压负移。证明阈值电压负移由外沟道渗透到内沟道的电场梯度产生,用自洽能带计算方法可算得漏电压引起的阈值电压负移。提出使用能带剪裁优化设计异质结构来抑制DIBL的新理念。同有限元变分软件的类MESFET模拟相比,新能带计算软件可以求得电荷控制中的量子行为。由此提出编制异质结场效应管模拟软件的设想。

Starting from the self-consistent solution of the two-dimensional Poisson equation and Schrödinger equation,the calculation software for calculating the channel energy band,electron gas density and quantum capacitance under different gate and drain voltages in GaN HFETs was developed,with which the charge control and DIBL of field effect transistors were studied.In the cal⁃culation of heterojunction channel wells,the electron gas density and quantum capacitance calculated by changing the gate voltage are consistent with the C-V experimental test results,which proves that solving the Schrodinger equation is the effective method for studying the charge control of the hetero⁃junction FET.After considering the electric field gradient penetrating from the outer channel to the in⁃ner channel,the electron gas density of the field effect transistor and quantum capacitance are calculat⁃ed.The quantum capacitance calculated by the field effect transistor simulation is consistent with the gate-source and gate-drain capacitance measured in the experiment.The inner channel energy bands under different gate,drain voltages and electric field gradient penetration are studied,and it is found that the electric field gradient penetration induced by the drain voltage causes the inner channel energy band to bow down,resulting in a negative shift of the threshold voltage.It is proved that the negative shift of the threshold voltage is caused by the electric field gradient that penetrates from the outer chan⁃nel to the inner channel.Using self-consistent energy band calculation method,the negative shift of threshold voltage caused by drain voltage is calculated.A new concept of using band tailoring to opti⁃mize the design of heterogeneous structures to suppress DIBL is proposed.Compared with the MES⁃FET-like simulation of the finite element variational software,the new energy band calculation soft⁃ware obtains the quantum behavior in charge control.Therefore,the idea of compiling simulation soft⁃ware for heterojunction FET is proposed.