Determination of free hole concentration in ferromagnetic Ga1−xMnxAs using electrochemical capacitance–voltage profiling

We demonstrate that electrochemical capacitance–voltage profiling can be used to determine the free hole concentration in heavily p-type doped low-temperature-grown GaAs films. This provides a simple and reliable method for measuring the hole concentration in ferromagnetic ${\mathrm{Ga}}_{\text{1−x}}{\mathrm{Mn}}_x\mathrm{As}$ semiconductor alloys. The method overcomes the complications that arise from the anomalous Hall effect term which affects standard transport studies of carrier concentration in conducting ferromagnetic materials. Specifically, we find that the maximum Curie temperature of about 111 K found for our ${\mathrm{Ga}}_{\text{0.91}}{\mathrm{Mn}}_{\text{0.09}}\mathrm{As}$ samples corresponds to a hole concentration of ${10}^{21}\hspace{0.17em}{\mathrm{cm}}^{\text{−3}}.$