Growth of type II strained layer superlattice, bulk InAs and GaSb materials for minority lifetime characterization

We have examined the growth of strained layer superlattice (SLS) structures for the purpose of characterizing and improving the minority carrier lifetime. Structures with different SL periods but with same absorption wavelength were first studied. Despite a doubling of the number of interfaces per thickness unit, no significant change was seen in the carrier lifetime. This observation points away from the interfaces as the location of lifetime limiting defect centers. To gain further insights into the spatial location of the defect centers, a series of binary InAs and GaSb layers grown with different substrate temperatures, were studied. We found that higher growth temperatures were beneficial for both binaries, although the improvement for GaSb was less than that of InAs. The substrate temperature was also varied in SLS structures and characterized with high-resolution x-ray diffraction. By using the peak width from the SLS zero-order diffraction as a figure of merit, we found a shallow growth window of ∼±20° around an optimum temperature of 440 °C. Outside this temperature window the material quality deteriorated very rapidly. Unfortunately, the substrate temperatures that would provide an improvement in the binary lifetimes fall mainly above the SLS growth window, thus limiting this parameter as a means of improving lifetimes in the SLS. A model that qualitatively relates bulk and SLS lifetimes through native defects is proposed and strategies for improving the lifetimes are discussed.