A 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 a spectroscopic measurement of the hole density in four Ga1-xMnxAs samples (x=0, 0.038, 0.061, and 0.083) at room temperature using a 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 class of ``spintronic'' semiconductor materials.
Physical Review B
- Pub Date:
- July 2002
- Magnetic semiconductors;
- III-V and II-VI semiconductors;
- Condensed Matter - Materials Science
- two-column format 5 pages, 4 figures, to appear in Physical Review B