Microscopic characterization of InAs/In0.28GaSb0.72/InAs/AlSb laser structure interfaces -: art. no. 245311

We have used cross-sectional scanning tunneling microscopy (XSTM) and transmission electron microscopy (TEM) to study InAs/In0.28Ga0.72Sb/InAs/AlSb strained-layer heterostructures designed for use in infrared lasers. The samples came from the same material previously characterized by photoluminescence (PL) and x-ray diffraction [M. J. Yang et al., J. Appl. Phys. 86, 1796 (1999)]. Several structures grown at different temperatures and with either III-As or III-Sb-like interfacial bonds have been characterized. Analysis of high-resolution TEM images finds the same degree of interfacial roughness (similar to1 ML) for both III-As and III-Sb interfacial bonded heterostructures, despite significantly greater PL intensity in the latter. We also implement and compare two different methods for analyzing the interfacial roughness using XSTM; both show that the crucial InAs/InGaSb interface is rougher in the samples grown at high temperature. Even in samples grown at the optimal temperature (similar to 440 degreesC), XSTM reveals intermixing at the AlSb-on-InAs interfaces, as well as unexpected differences in the interfacial bond types at the InAs-on-AlSb vs AlSb-on-InAs interfaces. Whereas all layers grown at or below the optimal growth temperature appear defect-free in TEM, threading dislocations are observed in samples grown at higher temperature.