GaMnAs: Position of Mn-d levels and majority spin band gap predicted from GGA-1/2 calculations

Abstract

Among all magnetic semiconductors, GaMnAs seems to be the most important one. In this work, we present accurate first-principles calculations of GaMnAs within the GGA-1/2 approach: We concentrate our efforts in obtaining the position of the peak of Mn-d levels in the valence band and also the majority spin band gap. For the position of the Mn-d peak, we find a value of 3.3 eV below the Fermi level, in good agreement with the most recent experimental results of 3.5 and 3.7 eV. An analytical expression that fits the calculated Eg(x) for majority spin is derived in order to provide ready access to the band gap for the composition range from 0 to 0.25. We found a value of 3.9 eV for the gap bowing parameter. The results agree well with the most recent experimental data.

Polytypism in ZnS, ZnSe, and ZnTe: First-principles study

“…This approach allows the inclusion of spin-orbit interaction in a rather easy manner, which usually works very well and gives very good results for the band gaps, bandwidths, and band dispersions [74][75][76][77][78][79][80][81]. In addition, it compares well with results of the GW quasiparticle (QP) approach [26,72,[82][83][84].…”

Digital magnetic heterostructures based on GaN using GGA-1/2 approach

“…In the LDA þ U method, the U parameter is not known in principle and should be obtained by fitting the results to some reported measurements. 26 For example, the U needed for Mn-d orbital is not well defined: Some studies report a value of 3 eV, 27 while others claim it to be 4 eV. 28 Moreover, the LDA þ U cannot be applied to all magnetic compounds, for example, GaMnN is not well described by this approach.…”

“…The trimming is made by means of a cutting function with a parameter "CUT," which is determined variationally by making the bandgap extreme. 26 In Table I, for the seven DMHs, we show the energy difference between FM and AFM states (DE) and the magnetic moment per TM atom (l), calculated within SDFT-GGA approach. Only GaN/V and GaN/Cr present a FM ground state.…”

“…We chose the GGA-1/2 (or its analogue, LDA- 1/2) because it is a parameter-free method and has been shown to accurately predict excited states for bulk semiconductors, alloys, and interfaces, at a very small computational price. [32][33][34][35][36][37] Besides, GGA-1/2 also furnishes correct descriptions for magnetic semiconductors, being already applied successfully to GaMnAs 26 and Cr-doped InN. 38 This procedure is inspired by the old Slater transition state technique for atoms, shown to be equivalent to the inclusion of the selfenergy of the quasi-particle.…”

Electronic- and band-structure evolution in low-doped (Ga,Mn)As

“…Quantitative analysis of that type of Raman spectra can provide important information on the free-carrier density in heavily doped semiconductors. A reliable method of determining hole concentration in (Ga,Mn)As layers, based on analysis of their Raman spectra, without applying large magnetic fields, which is required in the Hall-effect measurements for ferromagnetic materials in order to extract the ordinary Hall effect from the dominating anomalous Hall effect, was proposed by Seong et al 28 By examination of the relative Raman intensities of the LO-phonon and CPLP lines and their shift toward the TO-phonon position, and comparing them with the literature data, 27,28 we have estimated the hole concentrations of 0.5×10 19 …”