Temperature-induced instability of the threshold voltage in GaN-based heterostructure field-effect transistors

Temperature-induced instability of the threshold voltage in GaN-based heterostructure field-effect transistors (HFETs) and Al₂O₃– and ZrO₂–based metal-oxide-semiconductor (MOS) HFETs was investigated and their trapping effects were analyzed. A negative or positive threshold voltage shift was observed in the HFETs with a AlGaN or InAlN barrier, which indicates that electron or hole traps dominate in the barriers. A temperature dependence of the threshold voltage in the MOSHFETs exhibited two different regions. At lower temperatures, similarly as in the HFETs, traps in the barrier dominated. However, at temperatures above 100−150 °C the threshold voltage shift was more pronounced and connected with the oxide/insulator interface traps. The threshold voltage shift can be negative or positive if a Al₂O₃ or ZrO₂ gate insulator, respectively, is used. The results show that the temperature dependence of the threshold voltage can be controlled by the barrier layer composition and/or the gate insulator type. (paper)