Drain Current Density Over 1.1 A/mm in 2D Hole Gas Diamond MOSFETs With Regrown p++-Diamond Ohmic Contacts

We report two-dimensional hole gas (2DHG) diamond field-effect transistors (FETs) with microwave plasma chemical vapor deposition (MPCVD)-regrown p++diamond (B concentration ~ 1 × 1022/cm3) ohmic contacts. The heavily doped p++-diamond shows low ohmic contact resistance of 1.1 Q·mm, which is the lowest value reported in diamond to date. In addition, the p++-diamond with a TiC also offers much stronger metal adhesion when compared with previous Au/hydrogen-terminated diamond surfaces and is suitable for industrial use. Benefiting from the low contact resistance of the p++-diamond layer, a maximum drain current density of 1170 mA/mm and an ON-resistance of 8.9 Q·mm were demonstrated in a 2DHG diamond metaloxide-semiconductor FET with a 1 μm gate length. These results indicate that the regrown p++-diamond ohmic contacts will make it possible to realize further improvements in the maximum drain current density of 2DHG diamond FETs.