AIGaN Schottky characteristics after hybrid photo-enhanced wet and inductively coupled plasma etch

Abstract

AlGaN Schottky contact characteristics after hybrid photo-enhanced wet etch and Inductively coupled plasma etch (ICP) is studied. AlGaN was grown by MOCVD on sapphire substrate. KOH solution and 100mW/cm(2) UV illumination by Hg are lamp was used for photo-enhanced wet etch. Gas mixture of Cl-2 and N-2 was used for ICP etch. The Schottky metal used in this study is Ni/Au (100nm/100nm) and the Ohmic metal used is Al (100nm). Typical etch rates are 0.28nm/min and 265nm/min with a roughness of 0.6nm and 1.17nm for wet and dry etch respectively. The ICP process etches more rapidly but the etched surfaces are rougher when compared to the wet-etch process. After ICP etch at 600 watt for 60sec, the schottky diode has an ideality factor n=2.6, and the barrier height phi(B)=0.65 eV However, for the ICP etched sample followed by photo-enhanced wet chemical etch for 30mins, the sample has an ideality factor n=0.99, and the barrier height phi(B)=0.86 eV, and the breakdown voltage is recovered from 4V to 7.5V The study indicates that the wet chemical etch can remove the damage caused by ICP etching. Overall, the hybrid dry/wet etch process is a high etch rate process and cause very low damages on the etched surface.