The warpage of the GaN template grown by a HVPE with gallium droplet treatment was 13.8μm, which was reduced by 80.3% of the warpage for GaN template grown by conventional MOCVD and 43% of the warpage for GaN template grown by HVPE without gallium droplet treatment. The treatment of gallium droplets on sapphire was achieved by thermal evaporator at room temperature. The E2 high peak of GaN template with gallium droplet treatment appeared at 566.5/cm, whereas the E2 high peak of GaN template by MOCVD was positioned at 569.5/cm in the Raman scattering spectra. According to the frequency shifts of E2 high peak position for each template around 3/cm, the release of compressive stress of GaN template grown by HVPE with gallium droplet treatment was shown. In the study of FE-SEM and glow discharge spectroscopy, voids and concentration decline zones of gallium and aluminium in counter direction were formed at the interface between GaN epilayer and sapphire substrate during GaN growth by HVPE. It was expected that the decrease of warpage and stress for GaN template with gallium droplet treatment was caused by the formation of voids and concentration decline zones of gallium and aluminium. The etch pits density of GaN templates, having gallium droplet treatment, was around 8.5 x 107/cm2.

Reducing the Warpage and Dislocation Density of GaN Template Grown by HVPE with Gallium Droplet Treatment. Y.J.Choi, H.K.Oh, J.G.Kim, H.H.Hwang, H.Y.Lee, W.J.Lee, B.C.Shin, J.Hwang: Physica Status Solidi C, 2010, 7[7-8], 1770–4