GaN HFET中的能带峰势垒和跨导崩塌  

Peak Band Barrier and Transconductance Collapse in GaN HFET

作　　者：薛舫时[1] 杨乃彬[1] 陈堂胜[1] XUE Fangshi;YANG Naibin;CHEN Tangsheng(Science and Technology on Monolithic Integrated Circuits and Modules Laboratory,Nanjing Electronic Devices Institute,Nanjing,210016,CHN)

机构地区：[1]南京电子器件研究所微波毫米波单片集成和模块电路重点实验室,南京210016

出　　处：《固体电子学研究与进展》2022年第3期163-169,共7页Research & Progress of SSE

基　　金：国家自然科学基金资助项目(61874101);江苏省重点研发计划资助项目(BE2020007)。

摘　　要：考虑大沟道电流下外沟道局域电子气慢输运行为破坏沟道电中性,诱生空间电荷导致的能带峰势垒,提出了新的跨导崩塌模型。详细计算了不同栅压和不同沟道电流密度、即不同空间电荷密度下的场效应管能带。引入新的能带峰势垒和沟道电子跨越势垒的动态模型,解释了沟道打开过程中源电阻增大、沟道电子平均速度下降、大沟道电流下跨导下降等各类跨导崩塌行为,解释了场效应管沟道电子速度远低于异质结材料的缘由。运用沟道打开时的异质结充电和大沟道电流激励下空间电荷触发的能带峰势垒模型解释了跨导钟形曲线上升段中的电流崩塌和下降段中的跨导崩塌。深入研究了陷阱和局域电子气的相互作用,解释了可靠性加速寿命试验中的跨导曲线变化。沟道夹断的强负栅压应力产生内沟道逆压电缺陷,减弱栅电压对内沟道电子气的控制和沟道打开时跨导的上升斜率。沟道打开后的大电流应力使局域电子气与晶格碰撞产生热电子缺陷和空间电荷,抬高能带峰势垒引发外沟道堵塞,降低沟道电流,导致阈值电压正移。这一研究证明在场效应管直流和射频工作中的器件性能退化都是由陷阱同局域电子气相互作用产生的,开创了优化设计异质结能带来提高场效应管可靠性的新途径。最后讨论大沟道电流下能带峰势垒引发的外沟道堵塞和跨导崩塌在场效应管研发中的重要作用,提出了在空间电荷区上方设置专用的异质结鳍来平衡内、外沟道能带,解开场效应管中的电流崩塌、跨导崩塌、线性、器件性能退化及3 mm高频工作等难点。Considering that the slow transport behavior of the localized electron gas in the outer channel under large channel currents destroys the channel neutrality and induces the peak band barrier caused by the space charge,a new transconductance collapse model is proposed. The energy bands of the field effect transistors under different gate voltages and different channel current densities,that is,different space charge densities,are calculated in detail. The introduction of a new dynamic model of peak band barrier and channel electron crossing the barrier explains various transconductance collapse behaviors such as the increase of source resistance,the decrease of the average velocity of channel electrons,and the decrease of transconductance under large channel current,and it explains the reason why the electron velocity in the FET channel is much lower than that in the heterojunction material. The current collapse in the rising phase and the transconductance collapse in the falling phase of the transconductance bell curve are explained by the heterojunction charging during channel opening and the energy band peak potential barrier model of space charge triggering under large channel current excitation.The interaction between the traps and the local electron gases is deeply studied,from which the transconductance curve variation in the reliability accelerated life test is explained. The strong negative gate voltage stress under the channel pinch-off condition produces the inner channel reverse piezoelectric defect,which weakens the control of gate voltage on the inner channel electron gases and the rising slope of the transconductance at the opening of channel. After the channel is opened,the high current stress causes the local electron gases to collide with the crystal lattice to generate hot electron defects and space charges,which raise the peak band barrier to cause the outer channel to block. Decrease the channel current,resulting in a positive shift in the threshold voltage.This study proves that the device pe

关 键 词：跨导崩塌 能带峰势垒 能带畸变 局域电子气 陷阱和局域电子气的相互作用 沟道电子的速-场特性 钟形跨导曲线 异质结鳍 

分 类 号：TN386[电子电信—物理电子学]