Dynamic Characteristics of GaN MISHEMT With 5-nm In-Situ SiNx Dielectric Layer

A comprehensive study on dynamic characteristics of GaN MISHEMT with a 5nm-thick in-situ SiNx dielectric is presented. Effects of both negative and positive gate bias on threshold voltage instability were investigated and miniature threshold voltage shift was acquired. The slight shift was considered to be associated with the traps at the insulator/AlGaN interface and in the dielectric layer itself. Pulsed I-V measurements with various gate quiescent biases presented small current collapse (11%) and low enhancement of dynamic Ron for zero quiescent drain bias. When drain quiescent bias was strengthened to 20V, an increased dynamic Ron/static Ron ratio was identified but still limited to a low value of 1.24. The conduction reduction was in a good agreement with measurement results from drain current transient spectroscopy and possibly originates from trap states existed in the access region. Additional current collapse was observed in hard switching-on operation, resulted from energetic hot electrons accelerated by drain-source electrical field during the off-to-on step. The measurement results showed stabilized threshold voltage, a low dynamic Ron/static Ron ratio, and suppressed current collapse via employing a 5-nm thin in-situ SiNx layer in GaN MISHEMT, enabling it a promising solution for high-efficiency power switching applications.