Hole Transport in Impurity Band and Valence Bands Studied in Moderately Doped GaAs:Mn Single Crystals

We report on simple experiment on temperature-dependent Hall effect measurements in GaMnAs single crystalline samples with Mn composition estimated at 0.05-0.3 at.% which is slightly below the onset of ferromagnetism. Impurity band transport is visible for Mn compositions of ~0.3 at.% as a clear metallic behaviour. The results show interesting situation that the Metal-Insulator transition in GaAs:Mn occurs within the impurity band which is separated from the valence bands for Mn concentrations studied here. We also discuss on the equilibrium high temperature solubility limit of Mn in GaAs, unknown precisely in the literature.Comment: 9 pages, 2 figures, Proc. of 35th International School on the Physics of Semiconducting Compounds, Jaszowiec 2007, Poland, to appear in Acta Physica Polonica A (2007

Ferromagnetic semiconductor (In,Ga,Mn)As with Curie temperature above 100 K

We have grown (InyGa1-y)1-xMnxAs ferromagnetic semiconductor layers with Mn composition x up to 0.13 on InP substrates by molecular beam epitaxy. Near the lattice-matched composition, i.e., y ~ 0.53, the Curie temperature increases linearly with the ferromagnetically effective Mn composition x_eff, following the empirical equation T_C=1300x_eff. We obtained Curie temperatures above 100 K when x is relatively high (x>0.1; x_eff>0.08) and the hole concentration is in the order of 10^19 cm^-3.Comment: 13 pages, 3 figures; Applied Physics Letters, March, 200

Properties and Curie Temperature (130 K) of Heavily Mn-doped Quaternary Alloy Ferromagnetic Semiconductor (InGaMn)As Grown on InP

We have studied magnetic properties of heavily Mn-doped [(In0.44Ga0.56)0.79Mn0.21]As thin films grown by low-temperature molecular-beam epitaxy (LT-MBE) on InP substrates. The (InGaMn)As with high Mn content (21%) was obtained by decreasing the growth temperature to 190 degC. When the thickness of the [(In0.44Ga0.56)0.79Mn0.21]As layer is equal or thinner than 10 nm, the reflection high-energy electron diffraction (RHEED) pattern and transmission electron microscopy (TEM) show no MnAs clustering, indicating that a homogeneous single crystal with good quality was grown. In the magnetic circular dicroism (MCD) measurement, large MCD intensity and high Curie temperature of 130 K were observed.Comment: 3 pages, 5 figure

Electronic structure of In1−x_{1-x}Mnx_xAs studied by photoemission spectroscopy: Comparison with Ga1−x_{1-x}Mnx_xAs

We have investigated the electronic structure of the $p$-type diluted magnetic semiconductor In$_{1-x}$Mn$_x$As by photoemission spectroscopy. The Mn 3$d$ partial density of states is found to be basically similar to that of Ga$_{1-x}$Mn$_x$As. However, the impurity-band like states near the top of the valence band have not been observed by angle-resolved photoemission spectroscopy unlike Ga$_{1-x}$Mn$_x$As. This difference would explain the difference in transport, magnetic and optical properties of In$_{1-x}$Mn$_x$As and Ga$_{1-x}$Mn$_x$As. The different electronic structures are attributed to the weaker Mn 3$d$ - As 4$p$ hybridization in In$_{1-x}$Mn$_x$As than in Ga$_{1-x}$Mn$_x$As.Comment: 4 pages, 3 figure