LOW-TEMPERATURE PHOTOLUMINESCENCE CHARACTERISTICS OF CARBON-DOPED GAAS

We have analyzed low temperature (12 K) photoluminescence (PL) characteristics of carbon(C) doped GaAs epilayers. No traces of donor levels were observed in the PL spectra. This suggest that well-behaved carbon is incorporated as an acceptor into the GaAs lattice. The measured peak energy of the PL intensity distribution shifts to lower energy and the full width at half maximum (FWHM) increases with increasing hole concentration. We have obtained empirical relations for FWHM of PL intensity distribution in two distinct hole concentration regions. These relations are considered to provide a useful tool to determine free hole concentration in C doped GaAs by low temperature PL measurements. As the hole concentration is increased above 2 X 10(19) cm-3, a shoulder separated from the PL peak was observed in the PL spectra at E(g) + E(F), where E(g) is the band gap and E(F) is the Fermi energy. The shoulder became very prominent at 9.2 X 10(19) cm-3.