Spectroscopic determination of hole density in the ferromagnetic semiconductor Ga₁₋ₓMnₓAs

الأصل · EN

The measurement of the hole density in the ferromagnetic semiconductor Ga₁₋ₓMnₓAs 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 Ga₁₋ₓMnₓAs 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≤0.083, exhibiting a direct correlation to the observed Tc. The optical technique reported here provides an unambiguous means of determining the hole density in this important new class of ``spintronic'' semiconductor materials.