Improved device performance in in situ SiNx/AlN/GaN MIS-HEMTs with ex situ Al2O3 passivation at elevated temperatures

In the present work, the role of ex situ Al2O3 passivation in in situ SiNx/AlN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs) to boost device performance and thermal stability during the high-temperature operations has been thoroughly investigated. At room temperature (RT), the MIS-HEMT fabricated with an atomic layer deposited (ALD)-Al2O3 (MIS-HEMT B) exhibits higher maximum drain current (I-d,I-max), peak transconductance (g(m,max)), and lower subthreshold slope (SS) and gate leakage current compared to MIS-HEMT A fabricated without ex situ Al2O3, signifying the effectiveness of the ALD-Al2O3 layer to passivate severe surface states. Of note, when the temperature rises from 298 to 423 K, the values of I-d,I-max and g(m,max) decrease noticeably, while SS and gate leakage current increase considerably in both MIS-HEMTs A and B. However, MIS-HEMT B demonstrates a lower degradation rate in various device properties at 423 K compared to MIS-HEMT A, implying that ALD-Al2O3 passivation improves thermal stability. Additionally, ALD-Al2O3 passivation reduces the interface state density from 7.48 x 10(12) to 5.3 x 10(12) cm(-2) eV(-1), highlighting its critical role in improving overall device performance.