Relaxation of AlSb films grown on [001]-GaSb

Strain alters the electronic band structure and significantly affects the optical and electrical properties of semiconductors. Designed-in strains are often essential to the performance of laser and detector structures that rely upon strain-dependent band edge positions, carrier dispersions, and alignments. To take advantage of this beneficial strain, device structures are grown with thin semiconductor layers of precise thickness. Crystalline defects such as dislocations, grain boundaries, and stacking faults, negatively impact devices by providing easy paths for the diffusion of impurities and the transport of carriers. The defects also act as recombination centers for excess carriers and generally degrade both the electron and hole mobility. It is therefore important to understand the nature of strain relaxation in materials that are being incorporated into optoelectronic devices. We use TEM, x-ray, and electroreflectance to characterize the strain relaxation of AlSb epilayers grown on [001]-GaSb by MBE, as a function of epilayer thickness. The quality of the AlSb/GaSb interface is critical for the performance of quantum cascade laser devices.