Effect of Humidity and Electric Field on Reliability of GaN MISHEMT Test Structures

This study examines the effect of environmental factors and electric fields on the reliability of GaN MISHEMT test structures. Stress test results based on threshold voltage shifts reveal a correlation between relative humidity and the vertical electric field (gate voltage), whereby higher humidity and a stronger vertical field accelerate the degradation rate. Fur thermore, the TCAD simulations show that the aluminium (Al) concentration in the aluminium nitride (AlN) interlayer strongly
affects the vertical electric field strength, possibly accelerating degradation. Failure analysis reveals cracking of the AlGaN/GaN layer and delamination of the SiN passivation layer, both of which are caused by humidity and the vertical electric field.