Ferromagnetic Properties of Mn-Doped III–V Semiconductor Quantum Wells

Abstract

We investigate magnetic properties of In1−xMnxP and Ga1−xMnxN quantum wells in the mean-field approximation and show the difference between them. In the case of the In1−xMnxP, the dependence of the Curie temperature (Tc) on the hole density exhibits a step-like behavior, reflecting the effect of a two-dimensional Fermi (hole) gas, when the hole–hole exchange interaction is ignored. When we take into account the hole–hole exchange interaction, however, this behavior is broken by the appearance of peaks at the specific two-dimensional carrier densities, and Tc is substantially enhanced in this region. In the case of Ga1−xMnxN, the step-like behavior is obscure, and it appears that Tc increases rather continuously with the increasing two-dimensional (2D) carrier density. This shows very weak step-like behavior compared to other III-Mn-V DMS quantum wells, because the hole effective mass of Ga1−xMnxN is very large, and the large hole effective mass reduces the energy splitting due to the confinement effect. In a multi-heavy-valence-subband model, the Curie temperature of the In1−xMnxP quantum well is about 68 K with 6.5×1012 holes per cm2 and the Mn mole fraction x = 0.05 and the exchange constant Jpd = 0.15 eV nm3. The Curie temperature of the p-type Ga1−xMnxN quantum well can be above room temperature, unless the spin-exchange interaction integral is abnormally small.