Controlling impurity concentration profiles in p–n and n–p junctions by halide vapor phase epitaxy with n/p-separated nozzles

P–n and n–p junction structures with steep Mg concentration profiles were grown using a separated-nozzle halide vapor phase epitaxy (HVPE) reactor. In this reactor, n-type GaN and p-type GaN were grown at physically separated nozzles, enabling the independent control of impurity incorporation. The Mg concentration profile typically changes gradually owing to the absorption and residual presence of Mg on the reactor wall, which is known as the Mg memory effect. Supplying the Mg source to the separate nozzle for p-type GaN growth during n-type GaN growth results in a steep increase in Mg concentration at the onset of p-type GaN growth, effectively forming a steep p–n junction interface. Furthermore, by eliminating the Mg contamination from the nozzle used for n-type GaN growth, the Mg concentration was steeply decreased at the n–p junction interface. The accumulation of Fe at the p–n interface was observed in a conventional single-nozzle HVPE reactor, whereas no Fe accumulation was observed in the separated-nozzle HVPE reactor. A vertical p–n junction diode with avalanche breakdown capability was fabricated using the separated-nozzle HVPE reactor. From the results, the separated-nozzle HVPE reactor improves the Mg doping profile and suppresses the accumulation of Fe, demonstrating its potential for fabricating vertical power devices as well as a wide range of devices with p–n junctions, including optical and radio-frequency devices.