Spin-Polarized Tunneling as a probe of (Ga,Mn)As electronic properties

We present magnetic and tunnel transport properties of (Ga,Mn)As/(In,Ga)As/(Ga,Mn)As structure before and after adequate annealing procedure. The conjugate increase of magnetization and tunnel magnetoresistance obtained after annealing is shown to be associated to the increase of both exchange energy $\mathrm{\Delta }$${}_{exch}$ and hole concentration by reduction of the Mn interstitial atom in the top magnetic electrode. Through a 6x6 band k.p model, we established general phase diagrams of tunneling magnetoresistance (TMR) and tunneling anisotropic magnetoresistance (TAMR) $\mathit{\text{vs.}}$ (Ga,Mn)As Fermi energy (E${}_F$) and spin-splitting parameter (B${}_G$). This allows to give a rough estimation of the exchange energy $\mathrm{\Delta }$${}_{exch}$=6B${}_G$$\simeq$120 meV and hole concentration p$\simeq {1.10}^{20}$cm${}^{-3}$ of (Ga,Mn)As and beyond gives the general trend of TMR and TAMR $\mathit{\text{vs.}}$ the selected hole band involved in the tunneling transport.