Emissivity-correcting mid-infrared pyrometry for group-III nitride MOCVD temperature measurement and control

We report a pyrometer that operates at a mid-infrared wavelength range (7–8 μm), where sapphire substrates are opaque and the reactant gases are transparent. The pyrometer also employs a novel “self-reflectance” method of emissivity correction, whereby thermal emission from the sample serves as a radiation source to measure its emissivity. The instrument was installed on a multiwafer Veeco D-125 MOCVD system and used to measure the emissivity-corrected temperature at a variety of GaN and InGaN deposition conditions. For a series of InGaN multiquantum well growth, the pyrometer was used to control the surface temperature at the critical InGaN deposition step, resulting in improved control of the photoluminescence wavelength.