Photoluminescence of in_xGa_1-xAs_ySb _1-y epitaxial layers highly doped with tellurium grown by liquid phase epitaxy matched to GaSb

The influence of tellurium doping on the optical properties of In _xGa_1-xAs_ySb_1-y epitaxial layers has been studied by photoluminescence (PL) spectroscopy. Layers were grown by liquid phase epitaxy on (100) GaSb substrates highly resistive under lattice-matching conditions. PL measurements were carried out by exciting the sample with the 488-nm line of an Ar-ion laser and varying the exciting power in the range between 40 and 200 mW. PL spectra were also measured at different temperatures in the range between 15 and 300 K. For the low-doped sample the PL spectrum showed a narrow exciton-related peak centered at around 648.6 meV with a full width at half maximum (FWHM) of about 7 meV which is an evidence of the good crystalline quality of the epilayers and another dominant peak at 614 meV associated to band-to-acceptor. For higher Te-doping, the PL spectra showed the presence of band-to-band and donor-to-acceptor transitions which overlap as Te concentration increases. The peak of the PL band shifts to higher energies as Te doping increases due to a band-filling effect as the Fermi level enters into the conduction band. From the energy peak of the PL spectra and using a model that includes the band-filling and band-shrinkage effects due to the carriers, we have estimated the effective carrier concentration due to the doping with Te in the epilayers, in the range 10¹⁶ to 10¹⁷ cm ^-3.