CdZnTe graded buffer layers for HgCdTe/Si integration

To investigate the potential benefits of compositional grading for dislocation control in CdTe/Si growth, Cd_1−xZn_xTe buffer layers with x graded smoothly from 1 to 0 have been deposited on Si (211) surfaces. Growth has been characterized using reflection high-energy electron diffraction (RHEED), x-ray diffraction (XRD), and etch pit density measurements. XRD showed an increase in rocking curve full-width at half-maximum (FWHM) and global lattice tilt with decreasing x values. Tilt was also observed to increase as buffer growth temperature was increased. Final surface dislocation densities did not decrease below 7×10⁶ cm⁻². EPD surface dislocation measurements showed reduced dislocation densities and dislocation clustering along the and lines for CdTe cap layers grown on partially graded Cd_1−xZn_xTe buffer layers with slow compositional grading rates. Samples grown with faster grading rates showed higher final EPD values, with dislocations clustering along the and lines.