In-situ control of large area (11-22)-GaN growth on patterned r-plane sapphire

This report describes in-situ measurements of multi-wavelength reflectance, wafer curvature and growth temperature during epitaxy of semi-polar (11-22)-GaN on 100 mm diameter r-plane PSS. Reflectance transients at 405 nm can be correlated with the development of GaN facets prior to coalescence and with the final layer morphology after coalescence. It is shown that emissivity-corrected near-IR pyrometry may give deficient growth temperature readings on pockets with low reflecting patterned substrates. Near-UV pyrometry has been used to quantify wafer temperature depending on process parameters and wafer bow. In-situ curvature measurements reveal a tensile-strained growth mode for the GaN nucleation applied and additional curvature components due to a higher thermal gradient in growth direction than for planar growth. Room temperature wafer bow of 7 µm thick (11-22)-GaN on r-PSS is spherical and comparable to c-oriented layers.