Threshold Voltage Stability in AlGaN/GaN MIS-HEMT Structure Under Cryogenic Environment

The electrical behavior of AlGaN/GaN Schottky-gate high-electron mobility transistors (HEMTs) and metal-insulator–semiconductor HEMTs (MIS-HEMTs) at cryogenic temperatures ranging down to 10 K is investi- gated in this research. The well-known reliability issues in oxide transistors, such as current collapse and threshold voltage ( ${V}_{\text {TH}}$ ) variations, emphasize the necessity of such studies. A more pronounced ${V}_{\text {TH}}$ variation in MIS-HEMTs compared to Schottky-gate HEMTs is observed, which is attributed to the presence of acceptor-like defect states within the oxide layer. The negative ${V}_{\text {TH}}$ shift in MIS-HEMTs can be ascribed to the reduced thermionic emission of electrons. These findings are validated through bias temp- erature instability tests. These insights offer perspectives on the performance differences between the two transistor configurations in cryogenic environments.