Secondary ion mass spectrometry analysis of Mg doped GaN films prepared by hot wall epitaxy

Mg doped GaN films were prepared by hot wall epitaxy and Mg and oxygen concentrations were measured by secondary ion mass spectrometry (SIMS). Two kinds of doping methods were performed: one was modulation doping of Mg and another was continuous doping. The modulation doping was performed by flip-flop method in which growth was interrupted on the hot wall for impurity after every 15 nm thick growth of GaN and the continuous growth was performed by introducing Mg impurity into the GaN hot wall using Mg3N2 source. SIMS analysis of modulation doped GaN films showed clear periodic Mg distribution even though the growth temperature is as high as 1000°C. Background oxygen concentration of modulation doped GaN films were of order of 1018 cm−3 and that of continuous growth was one order of magnitude lower than that of modulation doping. The oxygen concentration increased with the increase of Mg impurity concentration both for modulation doping and continuous doping. The oxygen concentration for continuous growth was restricted to one order of magnitude lower than that of the Mg impurity concentration.