Analysis of Abnormal Current Rise Mechanism in GaN-MIS HEMT With Al2O3/Si3N4 Gate Insulator Under Hot Switching

As a transmitter power amplifier (PA), the electrical output characteristics of gallium nitride (GaN) high electron mobility transistors (HEMTs) are closely related to the drain current versus drain voltage (
${I}_{d}$
–
${V}_{d}$
) characteristics. Any abnormalities in the
${I}_{d}$
–
${V}_{d}$
characteristics will seriously affect device performance. Therefore, many groups have investigated the kink effect of GaN HEMTs. One of the commonly used measurement methods of the kink effect is the
${I}_{d}$
–
${V}_{d}$
forward and reverse sweep. In this study, we used the same method for Al
₂
O
₃
/Si
₃
N
₄
–AlGaN/GaN metal–insulator–semiconductor HEMT (MIS HEMT) devices. We found that not only did the kink effect occurred but
${I}_{d}$
also increased abnormally during the reverse sweep and after a series of electrical measurements. At the end of the forward sweep, impact ionization caused by a high
${V}_{d}$
generated electron–hole pairs and some holes accumulated under the gate region, which caused the negative shift of the threshold voltage (
${V}_{\text{Th}}$
), leading to an abnormal increase in
${I}_{d}$
during the reverse sweep.