Enhancement-mode AlN/GaN/AlN XHEMTs

We observe a 2D hole gas at room temperature in an as-grown, undoped 10 nm coherently strained GaN layer within an AlN/GaN/AlN heterostructure grown on bulk AlN by MBE. Analogous to the inversion channel in silicon MOSFETs, we grow n ++ GaN source/drain regions and observe the p-GaN channel turns n-type under a positive gate voltage on a MOS gate overlapping the channel, achieving normally-off enhancement-mode n-channel transistor operation. We present the design principles to achieve E-mode AlN/GaN/AlN XHEMTs. The structure can also be realized on silicon, SiC, or sapphire to exploit the ultrawide bandgap of AlN while significantly reducing gallium consumption.