Measurement of [N] and T-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, and temperature, T; however, conflicting results have been observed using cyclotron resonance and thermomagnetic measurements. Using thermopower and Hall measurements, in conjunction with assumptions of parabolic bands and Fermi-Dirac statistics, we determined the T-dependence of the electron effective mass of GaAs$_{1-x}$N$_{x}$, in comparison with that of GaAs. Measurements of the T-dependent Seebeck coefficient, S, for N compositions ranging from x=0 to 0.0100, reveal a decrease in dS/dT with increasing x. For GaAs, the free carrier concentration, [n], is independent of T. In all other cases, [n] increases (decreases) with T (x). For GaAs, the effective mass decreases from 0.06m$_{0}$ at 140K to 0.052m$_{0}$ at 300K, similar to literature reports.$^{4}$ For GaAsN, the effective mass apparently increases (decreases) with x (T), ranging from 0.1m$_{0}$ to 0.16m$_{0}$ at 140K, with values 14{\%} (40{\%}) lower for x=0.0075 (x=0.0100) at 300K.