CORRELATION BETWEEN THE PHOTOREFLECTANCE RESPONSE AT E1 AND CARRIER CONCENTRATION IN N-GAAS AND P-GAAS

We investigated the photoreflectance (PR) response of metalorganic chemical vapor deposition-grown n- and p-type GaAs at the higher-energy transition E1 (almost-equal-to 2.9 eV). The doping level range of interest was 2 x 10(16) -4 x 10(18) cm-3 for Si:GaAs and 6 x 10(16) - 1 x 10(19) cm-3 for Zn:GaAs. Both the position and the broadening parameter, GAMMA-1, of the E1 transition within the doping concentration range were investigated. The evaluation of GAMMA-1's, based on the curve fitting of the PR response and the Kramers-Kronig analyzed data reveal a nearly linear relation between GAMMA-1 and the logarithm of the carrier concentration. This observation has the potential application for contactless determination of carrier concentration in moderate and heavily doped nanoscale films. Secondary-ion mass spectroscopy measurements show that there is relatively large compensation in Si:GaAs samples, but it does not correlate with the broadening of the E1 structure.