Photoluminescence of liquid-phase epitaxial Te-doped GaSb

Abstract

The photoluminescence (PL) spectra of Te-doped GaSb epitaxial layers grown from Ga-rich solutions by liquid-phase epitaxy have been studied in the electron concentrations from 8×1015 to 4×1018 cm−3. The electron concentration can be accurately controlled by varying the growth temperature and adding the polycrystalline Te-doped GaSb to replace half or all the undoped GaSb starting material in the growth solution. The dependence of line position, line intensity, spectral shape, and broadening on the doping level, power excitation, and temperature has been investigated in detail. At concentrations as low as 1×1016 cm−3, the GaSb sample has become degenerate because of the small effective mass of electrons and the broad band consisting of five partially resolved line dominates the low-temperature PL spectra. At concentrations above 1×1018 cm−3, the 19 K PL spectra is mainly dominated by the sub-band-gap, substrate-induced line A′ at 775.8 meV which is enhanced by the scattering of light off the back surface. This line A′ is direct evidence for the band-gap shrinkage at high doping level. This is the first report to present the detailed luminescence lines in the PL spectra of the Te-doped GaSb samples.