Normally-off AlGaN/GaN heterostructure junction field-effect transistors with blocking layers

In this study, normally-off AlGaN/GaN heterostructure junction field-effect transistors (HJFETs) with p-GaN cap layer were reported, in which intrinsic GaN were proposed as blocking layers between the p-GaN cap layer and the AlGaN layer to alleviate the Mg diffusion. It demonstrates that the p-GaN gated devices present negative shift in the threshold voltage but larger output current density with the increasing thickness of the blocking layer. We found that a 20 nm blocking layer can efficiently block the Mg diffusion into the AlGaN/GaN heterostructure and a channel mobility of 1200 cm2V−1s−1 was obtained. This value is comparable to the result obtained from a conventional AlGaN/GaN heterostructure, which means that the p-GaN cap shows no obvious degradation on channel mobility owing to the introduction of the blocking layer. The electrical performance of the recess region (without p-GaN cap) also confirm the channel degradation which can mainly ascribed to the Mg diffusion.