晶格匹配InAlN/GaN HEMTs栅极电流击穿行为研究

Study on Gate Current Breakdown Behavior of Lattice-matched InAlN/GaN HEMTs

相较于传统AlGaN/GaN HEMTs,采用晶格匹配In0.17Al0.83N/GaN异质结可有效消除逆压电效应引发的器件可靠性问题,而且沟道二维电子气密度更高,更适合射频微波通信应用。然而,In0.17Al0.83N/GaN HEMTs的外延片材料往往存在较高的位错密度,大幅度降低了器件的击穿场强。结合栅极偏压步进应力和微光显微技术,研究晶格匹配InAlN/GaN HEMTs的栅极电流击穿过程与机制,结果发现过激Fowler-Nordheim(FN)电流是器件击穿的主要原因。来自栅极的电子在高电场作用下发生FN隧穿成为高能热电子,它们会在异质结界面释放能量,导致该处形成大量新结构缺陷,同时InAlN材料本身固有可导缺陷密度相对较高,故当缺陷密度增加并达到某一临界值时,便会立刻发生瞬态静电释放,即电流热击穿。

Compared with AlGaN/GaN HEMTs,the lattice-matched In0.17Al0.83N/GaN heterojunction can effectively eliminate the device reliability problems caused by the inverse piezoelectric effect,and the two-dimensional channel electron gas density is higher,which is more suitable for RF microwave communication applications.However,the epitaxial wafer material often has a high dislocation density,which greatly reduces the breakdown field of the device.The gate current breakdown process and mechanism of lattice-matched InAlN/GaN HEMTs are studied in this paper by combining the gate bias step stress test and emission microscopy.The results show that the excessive FowlerNordheim tunneling current is mainly responsible for the breakdown behavior.The electrons from the gate tunnel into the barrier surface layer under the action of high electric field and become the high-energy hot electrons.They will release energy at the heterojunction interface,resulting in a large number of new structural defects.At the same time,InAlN material has relatively high inherent conductive defect density,when the defect density increases and reaches a certain critical value,the transient electrostatic discharge will occur immediately,namely the catastrophic thermal breakdown.