Growth and optimization of InxGayAl1−x−ySb buffer layers for electronic and optoelectronic applications

In(x)GayAl(1-x-y)Sb alloys have been grown by molecular beam epitaxy for use as a buffer layer for growing semiconductors on GaAs substrates with lattice constants beyond that of AlSb. This is an extension of the use of In(x)GayAl(1-x-y)Sb alloys to accommodate for the lattice mismatch with semi-insulating GaAs substrates. The growth of In0.21Ga0.19Al0.6Sb with a 6.2 angstrom lattice constant on semi-insulating GaAs substrates is the focus of this work. Several measures of the quality of a 1 mu m-thick In0.21Ga0.19Al0.6Sb layer improved when the growth temperature was increased from 460 to 600 degrees C. Atomic force microscopy root-mean-square values decreased from 2.9 to 1.8 nm and the peak-to-valley values decreased from 17.7 to 9.7 nm. In addition, double crystal x-ray diffraction omega-2 Theta spectra linewidths decreased from 568 to 482 arc sec. At the lower growth temperatures, several photoluminescence (PL) peaks associated with radiative recombination from regions with different alloy compositions were found. However, on increasing the growth temperature a single PL line was observed, strongly suggesting a more uniform alloy composition.