In-polar InN growth diagram by MOVPE

Abstract

The structural properties of wurtzite (WZ) In-polar InN layers grown by metal-organic vapor phase epitaxy (MOVPE) on GaN (0001) templates were systematically studied by varying the growth temperature (380–565 °C) and pressure (600–1500 hPa). WZ-phase InN layers were predominantly obtained across the entire temperature range. At high temperatures (TG > 500 °C), metallic In precipitated through thermal decomposition of InN. In contrast, at low temperatures (TG < 400 °C), In droplets formed on the growth surface and incorporation of zinc-blende (ZB) InN occurred as a result of insufficient NH3 activation. Increasing the growth pressure suppressed void formation near the InN/GaN interface due to InN decomposition in the high-temperature regime and suppressed both In droplet formation and ZB phase incorporation in the low-temperature regime. Thus, higher growth pressure not only inhibited InN decomposition but also promoted NH3 activation, thereby enhancing the effective V/III ratio. These results demonstrate that pressurized MOVPE expands the viable temperature window for In-polar InN growth. An evaluation of the crystallinity of InN confirmed that the crystal orientation improved as a result of suppression of metallic In precipitation and phase mixing as well as a reduction in threading dislocations. The growth diagram and crystallinity optimization guidelines presented in this study will facilitate the development of improved growth processes for InN-based device applications.