Control of impurity concentration in N-polar (0001¯) GaN grown by metalorganic vapor phase epitaxy

Unintentional impurity incorporation in N-polar GaN films grown by metalorganic vapor phase epitaxy (MOVPE) was investigated. The influences of growth conditions on the impurity concentration, electrical properties, and optical properties were discussed. Secondary-ion mass spectroscopy showed that both concentrations of carbon and oxygen were changed by growth conditions. With decreasing H₂/(H₂ + N₂) ratio, the carbon concentration increased, while the oxygen concentration decreased. At higher V/III ratios, the oxygen concentration decreased. Nitrogen-rich carrier gas and a high V/III ratio can decrease oxygen incorporation in the N-polar GaN epitaxial layer. The growth parameters discussed in this study are concluded to affect the adsorption/desorption properties of impurities. Based on these results, the electrical properties of N-polar III-nitrides can also be controlled by choosing the appropriate MOVPE growth conditions. This technology will lead to improvements in N-polar III-nitride-based device performance.