Abstract
Process chemical potential control (CPC) and dislocation reduction were implemented to control oxygen concentration in N-polar GaN layers grown on sapphire substrates via metal organic chemical vapor deposition (MOCVD). Process CPC offers a systematic and predictive framework for MOCVD experimental design relating the universal thermodynamic parameter, supersaturation directly to oxygen incorporation in N-polar GaN. As process supersaturation was changed from ~30 to 3,400, the formation energy of the oxygen point defect increased, which resulted in a 25-fold decrease in oxygen incorporation. Reducing dislocations by approximately a factor of 4 (to ~10^9 cm^-3) allowed for further reduction of oxygen incorporation to the low-10^17 cm^-3 range. Smooth N-polar GaN layers with low oxygen content were achieved by a two-step process, whereas first a 1 µm thick smooth N-polar layer with high oxygen concentration was grown, followed by low oxygen concentration layer grown at high supersaturation.
Sputter deposition of Mo-alumina cermet solar selective coatings: Interrelation between residual oxygen incorporation, structure and optical properties
