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*J(pd)(2) (where m* is the hole effective mass and J(pd) is the Kondo like hole/local-moment coupling), and the critical temperature T-c. 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.