Impurity Band Conduction in a High Temperature Ferromagnetic Semiconductor

Burch, K. S.; Shrekenhamer, D. B.; Singley, E. J.; Stephens, J.; Sheu, B. L.; Kawakami, R. K.; Schiffer, P.; Samarth, N.; Awschalom, D. D.; Basov, D. N.

Impurity Band Conduction in a High Temperature Ferromagnetic Semiconductor

Authors

Description

The band structure of a prototypical dilute ferromagnetic semiconductor, Ga$_{1-x}$Mn$_{x}$As, is studied across the phase diagram via optical spectroscopy. We prove that the Fermi energy ($E_{F}$) resides in a Mn induced impurity band (IB). This conclusion is based upon careful analysis of the frequency and temperature dependence of the optical conductivity ($σ_{1}(ω,T)$). From our analysis of $σ_{1}(ω,T)$ we infer a large effective mass ($m^*$) of the carriers, supporting the view that conduction occurs in an IB. Our results also provide useful insights into the transport properties of Mn-doped GaAs.
4 pages, 4 figures