INTEGRATED IN-SITU WAFER AND SYSTEM MONITORING FOR THE GROWTH OF CDTEZNTE/GAAS/SI FOR MERCURY CADMIUM TELLURIDE EPITAXY/

Reproducible improvements in the metalorganic vapor phase epitaxy (MOV PE) grown CdTe buffer quality have been demonstrated in a horizontal r ectangular duct silica reactor by the use of integrated in situ monito ring that includes laser reflectometry, pyrometry, and Epison concentr ation monitoring. Specular HeNe laser reflectance was used to in situ monitor the growth rates, layer thickness, and morphology for both ZnT e and CdTe. The substrate surface temperature was monitored using a py rometer which was sensitive to the 2-2.6 mu m waveband and accurate to +/-1 degrees C. The group II and group VI precursor concentrations en tering the reactor cell were measured simultaneously using two Epison ultrasonic monitors and significant variations were observed with time , in particular for DIPTe. The surface morphology and growth rates wer e studied as a function of VI/II ratio for temperatures between 380 an d 460 degrees C. The background morphology was the smoothest for VL/II ratio in the vicinity of 1.5-1.75 and could be maintained using Epison monitors. Regularly shaped morphological defects were found to be ass ociated with morphological defects in the GaAs/Si substrate. The x-ray rocking curve widths for CuKalpha (531) reflections were in the range of 2.3-3.6 are-min, with no clear trend with changing VI/II ratio. X- ray topography images of CdTe buffer layers on GaAs/Si showed a mosaic structure that is similar to CdTe/sapphire substrates. The etch pit d ensity in Hg1-xCdxTe layers grown onto improved buffer layers was as l ow as 6 x 10(6) cm(-2) for low temperature MOVPE growth using the inte rdiffused multilayer process.