High ION and ION/IOFF Ratio Enhancement-Mode Buried p-Channel GaN MOSFETs on p-GaN Gate Power HEMT Platform

Enhancement-mode (E-mode) buried p-channel GaN metal-oxide-semiconductor field-effecttransistors (p-GaN-MOSFET's) with threshold voltage (V-TH) of -1.7 V, maximum ON-state current (I-ON) of 6.1 mA/mm and I-ON/I-OFF ratio of 107 are demonstrated on a standard p-GaN/AlGaN/GaN-on-Si power HEMT substrate. An oxygen plasma treatment (OPT) was deployed to the gated p-GaN region where a relatively thick (i.e. 31 nm) GaN is retained without aggressive gate recess. The OPT converts the top portion of the GaN layer to be free of holes so that only the bottom portion remains p-type while being spatially separated from the etched GaN surface and gate-oxide/GaN interface. As a result, E-mode operation is enabled while a high-quality p-channel is retained. Multi-energy fluorine ion implantation was implemented for planar isolation of GaN p-channel FETs with mesa edges and sidewalls eliminated. Consequently, high I-ON/I-OFF ratio is obtained.