Enhancing the thermal stability of active contacts in AlGaN/GaN high electron mobility transistors with chemical vapor deposited carbon (C) films

This study investigates the long-term thermal stability (4 h at 300 °C) of active contacts in high electron mobility transistor (HEMT) devices with and without 10 nm-target thickness chemical vapor deposition (CVD) carbon (C) layers, utilizing in-situ resistance measurements. The thermal stability of the HEMT devices was investigated over the temperature range of 150–300 °C, employing sputtered 30 nm Ti/150 nm Al/30 nm Ti/30 nm TiN (top) with Ohmic metal structures. The results indicate that the HEMT devices with the about 10 nm-thick CVD C layer exhibit superior long-term thermal stability compared to those without the CVD C layer, maintaining Ohmic contact behavior throughout the duration of the test. The increase in contact resistance without C films was 2 %, whereas with the C films, it was only 0.5 % after the 4 h-long thermal stability test at 300 °C.