Emissivity-correcting near-UV pyrometry for group-III nitride OMVPE

Fundamental chemistry and modeling of group-III nitride MOVPE

“…Briefly, the system uses one 2 00 wafer centered on the rotation axis, with temperature and reflectance measured near the center of the wafer. Absolute wafer temperature is measured using a near-ultraviolet (NUV) emissivity-correcting pyrometer (ECP) we developed [22]. The GaN MOVPE conditions are given in Ref.…”

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

“…Under these conditions measurement of the thermal emission signal and sample reflectance (or emissivity) must be done to a higher level of accuracy (as compared with short wavelength pyrometers). For example, given a 1% error in thermal emission signal at 750 1C the NUV pyrometer [28] yields a 0.3 1C error, while the MIR pyrometer yields a 10 1C error (factor of 30 worse).…”

“…We were fortunately able to use most of the data acquisition software and wafer indexing and synchronization hardware we developed for the NUV-ECP system [28], with only minor modifications. With the wafer carrier spinning at 500-1200 rpm we are able to measure and keep track of the MIR temperature and reflectance (as well as the 550 nm reflectance) of each of the three 2 00 sapphire wafers.…”

“…900-1000 nm) normally used for pyrometry [25][26][27]. The problem is particularly severe because the InGaN composition (and therefore emission wavelength) is extremely sensitive to temperature in the 700-800 1C range, with a slope of $1-2 nm/1C [28]. Owing to errors in existing temperature measurement techniques, process drifts of 10-20 1C are common, leading to devices that emit outside of the desired target wavelength window.…”

“…One solution is to detect thermal emission in the near-UV (NUV) region around 400 nm, where at high temperatures GaN is opaque. We have successfully built several versions of emissivitycorrecting pyrometers (ECP) using this approach [28] and a non-emissivity-correcting version is now being commercialized by LayTec GmbH [29]. While the NUV approach has a number of positive attributes, the technique suffers from extremely weak thermal emission signals in the 700-750 1C range where high In-content InGaN is typically grown.…”