Spectroscopic determination of hole density in the ferromagnetic semiconductor Ga${}_{1-x}$Mn${}_x$As

Abstract

The measurement of the hole density in the ferromagnetic semiconductor Ga${}_{1-x}$Mn${}_x$As is notoriously difficult using standard transport techniques due to the dominance of the anomalous Hall effect. Here, we report the first spectroscopic measurement of the hole density in four Ga${}_{1-x}$Mn${}_x$As samples ($x=0,0.038,0.061,0.083$) at room temperature using Raman scattering intensity analysis of the coupled plasmon-LO-phonon mode and the unscreened LO phonon. The unscreened LO phonon frequency linearly decreases as the Mn concentration increases up to 8.3%. The hole density determined from the Raman scattering shows a monotonic increase with increasing $x$ for $x\le 0.083$, exhibiting a direct correlation to the observed $T_c$. The optical technique reported here provides an unambiguous means of determining the hole density in this important new class of ``spintronic'' semiconductor materials.

two-column format 5 pages, 4 figures, to appear in Physical Review B

References in corpus (1)

• Effects of annealing time on defect-controlled ferromagnetism in Ga1-xMnxAs

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