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

Abstract

We report two-dimensional hole gas (2DHG) diamond field-effect transistors (FETs) with microwave plasma chemical vapor deposition (MPCVD)-regrown p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">++</sup> diamond (B concentration ~ 1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">22</sup> /cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ) ohmic contacts. The heavily doped p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">++</sup> -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 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">++</sup> -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 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">++</sup> -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 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">++</sup> -diamond ohmic contacts will make it possible to realize further improvements in the maximum drain current density of 2DHG diamond FETs.