Photoreflectance for in-situ monitoring of thin-film growth
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This paper discusses some recent developments in the use of the contactiess electromodulation technique of photoreflectance for the in-situ monitoring of thin-film growth at elevated temperatures by such methods molecular beam epitaxy (MBE), metalorganic chemical vapor deposition (MOCVD) and gas phase molecular beam epitaxy (GPMBE). The direct gaps (E) of GaAs, Ga082A1018As, InP and InGa1As (x = 0.07 and 0.16) have been measured to over 600°C. These temperatures are comparable to the growth condition for MBE, MOCVD and GPMBE. For these semiconductors E can be evaluated to 5 meV at these elevated temperatures. Thus, the temperature of GaAs and InP substrate material could be determined to Also the Al composition of GaAlAs and In content of InGaAs could be monitored during actual growth procedures. Results for GaAs and GaA1A5 have been obtained in an actual MOCVD reactor including rotating substrate and flowing gases. We have succeeded in obtaining the spectra of E of GaAs at 650°C in 30 seconds.