EXPERIMENTAL AND THEORETICAL PHOTOLUMINESCENCE STUDY OF HEAVILY CARBON-DOPED GAAS GROWN BY LOW-PRESSURE METALORGANIC CHEMICAL-VAPOR-DEPOSITION

Carbon (C) doped GaAs epilayers grown by low-pressure metalorganic chemical vapor deposition have been analyzed by photoluminescence as functions of hole concentration and temperature. We have obtained an empirical relation of the effective band gap shrinkage for C doped GaAs as a function of hole concentration, DELTAE(g) = -2.17 x 10(-8)p1/3. The temperature dependent band gap energy of C doped GaAs with a hole concentration of 9.0 x 10(19) cm-3 has been analyzed. The resulting band gap at 0 K is (1.422+/-0.005) eV. The photoluminescence spectra have been analyzed on the bases of the Halperin and Lax bandtail model and an effective energy dependent optical transition matrix element. We have shown that the intensity distribution position of the photoluminescence spectrum of the conduction band to the heavy hole valence band transition is clearly separated from the intensity distribution of the conduction band to the light hole valence band transition. The conduction band to the light hole valence band transition is very prominent in the photoluminescence emission spectra of heavily C doped GaAs, and particularly at low temperatures. We have suggested that the shoulder peak which appears on the higher energy side of photoluminescence spectra is mainly due to the conduction band to the light hole valence band transition. At room temperature, the shoulder peak disappears and the full width at half maximum of the photoluminescence spectra increases; this is in good agreement with experimental results.