Measurement of [N] dependence of electron effective mass in GaAsN

The electron effective mass of GaAs$_{1-x}$N$_{x}$ is predicted to be dependent on N-composition, x; however, conflicting results have been observed using cyclotron resonance and thermomagnetic measurements. Using room temperature thermopower and Hall measurements, in conjunction with assumptions of parabolic bands and Fermi-Dirac statistics, we determined the N composition dependence of the electron effective mass of GaAs$_{1-x}$N$_{x}$, in comparison with that of GaAs. Measurements of the Seebeck coefficient, S, for N compositions ranging from x=0 to 0.018, reveal a decrease in S with increasing x. The free carrier concentration, [n], for all GaAsN is lower than for GaAs. For GaAs, we extract an effective mass value of 0.052m$_{e}$, slightly lower than the literature value of 0.067m$_{0}$. For GaAsN, the effective mass apparently is in all cases greater than for GaAs but varies non-monotonically with x, revealing a minimum at x=0.010 and maxima at x=0.004 and 0.018. This non-monotonic dependence of m* on x cannot be explained with a simple band anti-crossing (BAC) model. Interestingly, this data is consistent with the predictions of Lindsay et al, suggesting the presence of resonances between N-related states and the GaAsN conduction band edge.