Impact of Buffer Charge on the Reliability of Carbon Doped AlGaN/GaN-on-Si HEMTs

Charge trapping and transport in the carbon doped GaN buffer of an AlGaN/GaN-on-Si HEMT have been investigated. Back-gating and dynamic RON experiments show how the onset of leakage in the strain relief layer at a lower field than that through the upper part of the structure can result in serious long-term trapping leading to current collapse under standard device operating conditions. Controlling current-collapse requires control of not only the layer structures and its doping, but also the precise balance of leakage in each layer.