ELECTRON EFFECTIVE-MASS IN DIRECT-BAND-GAP GAAS1-XPX ALLOYS

The electron effective mass of the conduction band in direct-band-gap GaAs1-xPx alloys (x < 0.4) is reevaluated. A direct determination of m* using the optically detected cyclotron resonance technique is presented for the low composition values. For higher x values the scattering times decrease because of alloying and it was not possible to carry out resonance experiments. Instead the diamagnetic shifts of the shallow-donor-to-acceptor recombination lines in magnetic fields up to 12 T were investigated. Within the framework of a simple perturbation approach the corresponding m*(x) values (0.17 < x < 0.44) could be deduced. The results are compared with a theoretical estimate based on the k.p theory. There is good agreement between theory and experiment, resulting in a new x dependence of the conduction-band mass in the direct-band-gap GaAs1-xPx alloys: m* = 0.067 + (0.06 +/- 0.003) x.