Photoluminescence studies in highly Te-doped Ga _1-x In _x As _y Sb _1-y epitaxial layers grown on GaSb by liquid phase epitaxy

GaSb-based semiconductors are being developed because of the possibility to grow materials with band-gap energies covering a substantial range of the medium infrared spectrum. In particular, GaInAsSb alloys can be grown epitaxially on GaSb and InAs substrates, resulting in semiconductor layers with band-gap energies in the range 0.8-4.3μm. In this work we present results on the study of the influence of tellurium doping on the optical properties of Ga _1-x In _x As _y Sb _1-y epitaxial layers through the low temperature photoluminescence (PL) spectroscopy. These quaternary layers were grown by liquid phase epitaxy on high resistivity (100) GaSb substrates under lattice-matching conditions. PL measurements were carried out by exciting the sample with the 488nm line of an Ar-ion laser and varying the exciting power in the range between 40 and 200mW. All PL measurements were done at 15K. Sample radiative emission was analyzed through an Acton monochromator and detected with an InSb infrared detector. The PL spectrum for the low-doped sample showed two emission bands corresponding to different bounded excitons and free-to-bound transitions; the assignation of each transition is accomplished by studying the behavior of the PL spectra with the excitation power. The increase in Te doping above the degeneracy limit results in the substantial broadening of the low temperature PL spectra. The individual lines due to the band-to-band transitions and band-to-acceptor transitions (A) completely overlap each other for those samples with the higher Te concentrations. Additionally, at very high Te concentrations, the luminescence band becomes highly asymmetric and shifts to higher energies, which is interpreted as due to a band-filling effect. We discuss these effects and their correlation to the free carrier density due to Te-doping.