Infrared photoluminescence of InAs/GaAs epilayers grown by molecular beam epitaxy

Low temperature IR photoluminescence (PL) spectroscopy has been performed on InAs/GaAs epilayers with the thickness of 0.4, 0.5, 0.75 and 1.5 micrometers grown by molecular bema epitaxy for potential use as active layers in InAs-based IR lasers. A bulk InAs grown by Bridgeman technique is included for comparison with InAs epilayers. For the bulk InAs, three broad near-band-edge emission peaks are observed at 417 meV, 403 meV, and 383 meV at 10 K. Temperature and excitation power dependence of PL intensity give evidence that they may be related to band-to-band and/or exciton emission, conduction band-to-acceptor, and DAP recombination, respectively. For InAs/GaAs epilayers, the PL intensities of emission peaks are much smaller and emission peaks appear at higher energy side with maximum shift of about 5 meV, compared with the bulk sample. This blue shift can be attributed to strain effect due to large lattice mismatch between InAs epilayers and GaAs subset rates. As the thickness of epilayer increases the peak shift becomes small, which implies that the strain effect is reduced.