Etching-induced damage in heavily Mg-doped p-type GaN and its suppression by low-bias-power inductively coupled plasma-reactive ion etching

Inductively coupled plasma-reactive ion etching (ICP-RIE)-induced damage in heavily Mg-doped p-type GaN ([Mg] = 2 × 10¹⁹ cm⁻³) was investigated by low-temperature photoluminescence (PL) and depth-resolved cathodoluminescence (CL) spectroscopy. From PL measurements, we found broad yellow luminescence (YL) with a maximum at around 2.2-2.3 eV, whose origin was considered to be isolated nitrogen vacancies (V_N), only in etched samples. The depth-resolved CL spectroscopy revealed that the etching-induced YL was distributed up to the electron-beam penetration depth of around 200 nm at a high ICP-RIE bias power (P_bias). Low-bias-power (low-P_bias) ICP-RIE suppressed the YL and its depth distribution to levels similar to those of an unetched sample, and a current-voltage characteristic comparable to that of an unetched sample was obtained for a sample etched with P_bias of 2.5 W. (author)