Electron effective mass in direct-band-gapGaAs1−xPxalloys

The electron effective mass of the conduction band in direct-band-gap ${\mathrm{GaAs}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{P}}_{\mathit{x}}$ alloys (x<0.4) is reevaluated. A direct determination of ${\mathit{m}}^{\mathrm{*}}$ 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 ${\mathit{m}}^{\mathrm{*}}$(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 ${\mathrm{GaAs}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{P}}_{\mathit{x}}$ alloys: ${\mathit{m}}^{\mathrm{*}}$=0.067+(0.06±0.003)x.