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Title: Temperature Measurement and Thermal Modeling of Substrates Used during III-Nitride MOVPE.


Abstract not provided.

; ;
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
Report Number(s):
DOE Contract Number:
Resource Type:
Resource Relation:
Conference: Proposed for presentation at the 18th International Conference on Metal Organic Vapor Phase Epitaxy held July 10-15, 2016 in San Diego, CA.
Country of Publication:
United States

Citation Formats

Creighton, James Randall, Coltrin, Michael E., and Figiel, Jeffrey J.. Temperature Measurement and Thermal Modeling of Substrates Used during III-Nitride MOVPE.. United States: N. p., 2016. Web.
Creighton, James Randall, Coltrin, Michael E., & Figiel, Jeffrey J.. Temperature Measurement and Thermal Modeling of Substrates Used during III-Nitride MOVPE.. United States.
Creighton, James Randall, Coltrin, Michael E., and Figiel, Jeffrey J.. 2016. "Temperature Measurement and Thermal Modeling of Substrates Used during III-Nitride MOVPE.". United States. doi:.
title = {Temperature Measurement and Thermal Modeling of Substrates Used during III-Nitride MOVPE.},
author = {Creighton, James Randall and Coltrin, Michael E. and Figiel, Jeffrey J.},
abstractNote = {Abstract not provided.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2016,
month = 8

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  • Here, growth rates and alloy composition of AlGaN grown by MOVPE is often very temperature dependent due to the presence of gas-phase parasitic chemical processes. These processes make wafer temperature measurement highly important, but in fact such measurements are very difficult because of substrate transparency in the near- IR (~900 nm) where conventional pyrometers detect radiation. The transparency problem can be solved by using a mid-IR pyrometer operating at a wavelength (~7500 nm) where sapphire is opaque. We employ a mid- IR pyrometer to measure the sapphire wafer temperature and simultaneously a near-IR pyrometer to measure wafer pocket temperature, whilemore » varying reactor pressure in both a N 2 and H 2 ambient. Near 1300 °C, as the reactor pressure is lowered from 300 Torr to 10 Torr the wafer temperature drops dramatically, and the ΔT between the pocket and wafer increases from ~20 °C to ~250 °C. Without the mid-IR pyrometer the large wafer temperature change with pressure would not have been noted. In order to explain this behavior we have developed a quasi-2D thermal model that includes a proper accounting of the pressure-dependent thermal contact resistance, and also accounts for sapphire optical transmission. The model and experimental results demonstrate that at most growth conditions the majority of the heat is transported from the wafer pocket to the wafer via gas conduction, in the free molecular flow limit. In this limit gas conductivity is independent of gap size but first order in pressure, and can quantitatively explain results from 20 to 300 Torr. Further analysis yields a measure of the thermal accommodation coefficients; α(H 2) =0.23, α(N 2) =0.50, which are in the range typically measured.« less
  • Data on the thermal conductivity of commercially available aluminum nitride substrates, over the temperature range of 20-500 K, is analyzed using the Klemens-Callaway model. Parameters in this model which include crystallite size and impurity concentration, are determined through a nonlinear least squares fitting routine. The resulting parameters are compared with values obtained from other experimental techniques such as scanning electron microscopy (SEM) and proton induced x-ray emission (PIXE). A graphical method has been developed for the estimation of impurity concentration and crystallite size from low temperature thermal conductivity data. 19 refs., 3 figs., 3 tabs.
  • Numerical analysis and experimental measurements of the flattening degree of plasma sprayed molybdenum and zirconia droplets deposited on different substrate materials are presented. Investigation is focused on the influence of rate of solidification and wetting angle on droplet spreading. In the numerical analysis, the Madejski-Zhang model with one-dimensional treatment of solidification as well as heat transfer in the melt, solidified splat and substrate is employed. A parametric study is conducted to examine the effect of droplet size, impact velocity, superheating of droplets, substrate temperature, thermal contact resistance, and wetting angle on the spreading of droplet and flattening degree. Results showmore » that the time scale for solidification can be as small as that for spreading and rate of solidification can greatly influence the flattening degree. A guideline for when the effect of wetting angle and surface tension on droplet deformation can be neglected is derived. A correlation for the relationship between the flattening degree and Reynolds number with the consideration of solidification is deduced, and a criterion for the effect of droplet solidification on impact dynamics to be negligible is given. The limitation of the assumption of isothermal substrate is discussed. The numerical predictions statistically agree well with the experimental data.« less
  • Raman spectra of the hexagonal phase of boron nitride to temperatures exceeding 2000/degree/C, have been recorded using a pulsed-excitation gated-detection method. Surface temperatures were determined during rapid sample heating from analysis of corrected Stokes/anit-Stokes intensity ratios and from shifts in the resonance frequency of the 1366 cm/sup /minus/1/ E/sub g/ mode. Successive spectra were acquired at time intervals as short as 33 msec corresponding to the pulse repetition frequency of the probe laser. Using this synchronous detection technique, the time evolution of graphite furnace temperature was determined from measured spectra. Results indicate nearly complete rejection of sample blackbody from themore » Raman scattered light at these high temperatures. A nearly linear relationship between the Eg resonance frequency and temperature was found. Phonon linewidths were also found to increase by a factor of three over this temperature range. 5 refs., 6 figs.« less