Correlating Device Behaviors with Semiconductor Lattice Damage at MOS Interface by Comparing Plasma-etching and Regrown Recessed-gate Al2O3/GaN MOS-FETs

Abstract We correlate electical behaviors of recessed-gate Al2O3/GaN MOS-FETs with the lattice damage at MOS interface region by directly comparing plasma-etching (inductively coupled plasma, ICP) and regrown (selective-area-growth, SAG) methods. Firstly the regrown AlGaN/GaN heterostructure are evaluated, showing high crystal quality and good 2DEG transport properties and reaching the level of as-grown one. Then based on the as-grown and regrown heterostructures, ICP and SAG E-mode MOS-FETs were fabricated, respectively. ICP MOS-FET suffers from negative shift of Vth, leaky gate current, large Vth hysteresis and current collapse, while SAG MOS-FET demonstrates stable and nondegradating device performances. Compared to SAG MOS interface, high interface-traps-density is deduced in ICP MOS interface which causes serious electron trapping effects. These traps are found to be related to the lattice damage of plasma-etching GaN accompanying a rough and disorder surface morphology and the increase of nitrogen-vacancy and Ga-O bonds, responsible for the abominable device behaviors. Step-flow surface morphology is preserved for SAG sample, which results in the high-quality MOS interface. The results reveal the impacts of lattice damage at MOS interface on GaN device behaviors and also provide a pathway to settle them down.