Compensation of n-type GaN

Compensation in Se-doped n-type GaN prepared by atmospheric pressure metalorganic vapor phase epitaxy was studied. Hydrogen selenide was the dopant source. The carrier concentration is linearly proportional to the H₂Se pressure for low partial pressures and proportional to the cube root at high partial pressures. Carrier concentrations as high as 6 × 10¹⁹ cm^-3 at 295 K were achieved. From Hall-effect measurements, the Se-doped GaN was shown to be highly compensated even for heavily n-type material. The defects responsible for the compensation were investigated using low-temperature photoluminescence. A strong acceptor-related transition at 3.447 eV at 15 K was observed in the heavily doped layer. The observed doping dependence of Se in GaN is attributed to compensation by triply charged vacancies which is consistent with recent theoretical calculations on defect formation in n-type material.