Highly homogeneous bulk-like 2′′ GaN grown by HVPE on MOCVD–GaN template

Abstract

We succeeded in preparing a 21-μm-thick GaN layer of high crystalline quality and with small in-plane stress on a 2′′ sapphire substrate by hydride-vapor phase-epitaxy (HVPE) in a vertical atmospheric-pressure reactor with a bottom-fed design. An ∼5-μm-thick GaN template layer grown by metalorganic chemical vapor deposition (MOCVD) was employed. At 1090 °C, the HVPE growth rate was gradually increased by a step increase of the HCl gas flow rate, and was as high as 21 μm/h in average. Superior lateral homogeneity of the HVPE material over the entire 2′′ wafer with regard to the crystalline quality and residual stress is proven by photoluminescence mappings of the main donor-bound exciton properties. Both the average in-plane stress and the free-electron concentration are found to be considerably reduced in the HVPE-grown material compared to the MOCVD-grown template.