LOW-TEMPERATURE GROWTH OF MIDWAVELENGTH INFRARED LIQUID-PHASE EPITAXY HGCDTE ON SAPPHIRE

Consistently low dislocation density midwavelength infrared (x = 0.31) liquid phase epitaxy HgCdTe epitaxial layers with excellent morphology were grown on 2 in. sapphire substrates (PACE-1) using a new low-temperature (420-degrees-C) Te melt process. Surface etch pit densities (EPDs) between 5 x 10(5) and 9 x 10(5) cm-2 were revealed using a previously reported chemical etch (J.S. Chen, US Patent No. 4897152) on a 20-layer sample set. Cross-sectional EPD profiles reveal a more rapid decrease of defects from the CdTe buffer layer interface as compared to conventionally grown (500-degrees-C) material. X-ray rocking curve widths from 43 to 66 arcsec were routinely observed. 77 K electron mobilities as high as 51 000 cm2/V-s were measured. Secondary-ion mass spectrometry profiles show a minimum of impurity gettering at the HgCdTe/CdTe buffer layer interface.