An in situ monitored and controlled etch process to suppress Mg memory effects in MOCVD GaN growth on Si substrate

Abstract

Mg is the most common p-type dopant in III-nitride devices and is becoming increasingly important in the design and development of transistors for power applications. The diffusion of Mg atoms to adjacent layers during growth has been a persistent problem. We report on a simple method involving in situ etching by hydrogen, the most commonly used carrier gas in nitride growth, for suppressing Mg diffusion. This method can be implemented during growth itself without removing the wafer from the chamber and can be controlled by in situ monitoring. A Mg concentration decay rate of 24 nm/dec, is reported for the etched sample compared to 160 nm/dec for the unetched one. An increase in 2DEG mobility in AlGaN/GaN HEMT structures on silicon substrate from 591 cm(2) V-?1 s(?1) for the unetched sample to 1214 cm(2) V(?1 )s(?1 )for the etched sample was observed. Capacitance?voltage studies to understand the effect of diffused Mg atoms on conduction channel are also reported.