Hole concentration in a diluted ferromagnetic semiconductor

We consider a mean-field approach to the hole-mediated ferromagnetism in III-V Mn-based semiconductor compounds in order to discuss the dependence of the hole density on that of Mn sites in Ga1-xMnxAs. The hole concentration, p, as a function of the fraction of Mn sites, x, is parametrized in terms of the product m*Jpd2 (where m* is the hole effective mass and Jpd is the Kondo-like hole/local-moment coupling), and the critical temperature Tc. By using experimental data for these quantities, we have established the dependence of the hole concentration on x, which can be associated with the occurrence of a re-entrant metal-insulator transition taking place in the hole gas. We also calculated the dependence of the Mn magnetization on x, for different temperatures (T), and found that as T increases, the width of the composition-dependent magnetization decreases dramatically, and that the magnetization maxima also decrease in magnitude, indicating the need for quality control of the Mn doping level in diluted magnetic semiconductor devices. (author)