PHOTOLUMINESCENCE STUDY OF HEAVILY TE-DOPED GAAS GROWN BY LIQUID-PHASE EPITAXY

Systematic studies of photoluminescence (PL) are used to characterize the heavily Te-doped GaAs layers with electron concentrations of 9.4 x 10(18)-2.3 X 10(19) cm-3. For the undoped layer with an electron concentration of 1 X 10(15) cm-3, the near-band-to-band transition is found to dominate the low-temperature PL spectra. While at concentrations above 10(18) cm-3, both the band filling as well as band tailing due to the carrier scattering with the ionized donor impurities and band shrinkage due to the exchange interaction between free carriers are considered to account for the observed luminescence behavior. The dependence of spectral shape and broadening on the doping level, excitation power and temperature has been investigated in detail. At concentrations above 1 X 10(19) cm-3, the low-temperature PL spectra is mainly dominated by the low energy, band-edge artifact peak B at 1.488 eV which passes through the substrate, reflects off the back surface, and is emitted from the epitaxial surface. The low-energy transition becomes stronger with doping due to the increase in the band shrinkage.