Influence of channel/back-barrier thickness on the breakdown of AlGaN/GaN MIS-HEMTs

The leakage current and breakdown voltage of AlGaN/GaN/AlGaN high electron mobility transistors on silicon with different GaN channel thicknesses were investigated. The results showed that a thin GaN channel was beneficial for obtaining a high breakdown voltage, based on the leakage current path and the acceptor traps in the AlGaN back-barrier. The breakdown voltage of the device with an 800 nm-thick GaN channel was 926 V @ 1 mA/mm, and the leakage current increased slowly between 300 and 800 V. Besides, the raising conduction band edge of the GaN channel by the AlGaN back-barrier lead to little degradation for sheet 2-D electron gas density, especially, in the thin GaN channel. The transfer and output characteristics were not obviously deteriorated for the samples with different GaN channel thickness. Through optimizing the GaN channel thickness and designing the AlGaN back-barrier, the lower leakage current and higher breakdown voltage would be possible. (paper)