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

摘要

Modulation photoreflectance spectroscopy and Raman spectroscopy have beenapplied to study the electronic- and band-structure evolution in (Ga,Mn)Asepitaxial layers with increasing Mn doping in the range of low Mn content, upto 1.2%. Structural and magnetic properties of the layers were characterizedwith high-resolution X-ray diffractometry and SQUID magnetometery,respectively. The revealed results of decrease in the band-gap transitionenergy with increasing Mn content in very low-doped (Ga,Mn)As layers withn-type conductivity are interpreted as a result of merging the Mn-relatedimpurity band with the host GaAs valence band. On the other hand, an increasein the band-gap-transition energy with increasing Mn content in (Ga,Mn)Aslayers with higher Mn content and p-type conductivity indicates theMoss-Burstein shift of the absorption edge due to the Fermi level locationwithin the valence band, determined by the free-hole concentration. Theexperimental results are consistent with the valence-band origin of mobileholes mediated ferromagnetic ordering in the (Ga,Mn)As diluted ferromagneticsemiconductor.