Determination of carrier concentration in Ga1-xMnx as using Raman spectroscopy

초록

Ga1-xMnxAs with Curie temperatures (T-c) as high as 110 K has recently emerged as an important spintronic semiconductor material. The ferromagnetism in this material arises from the exchange interaction between the free carriers (holes) generated by Mn doping and the Mn2+ ions. However, the accurate determination of the carrier concentration in Ga1-xMnxAs using standard transport techniques is extremely difficult because of the dominant anomalons Hall effect. We have performed spectroscopic measurement of the hole density in four Ga1-xMnxAs samples (x = 0, 0.038, 0.061, 0.083) 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 increase up to 8.3%. The hole density determined from the Raman scattering exhibits a direct correlation to the observed T-c providing an unambiguous means of determining the hole density in this important new class of ferromagnetic semiconductors.

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