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We study the growth and properties of the quaternary-alloy ferromagnetic semiconductor (In0.94−x,Gax,Fe0.06)Sb (x = 5%–30%; the Fe concentration is fixed at 6%) grown by low-temperature molecular beam epitaxy. Reflection high-energy electron diffraction patterns, scanning transmission electron microscopy lattice images, and x-ray diffraction spectra indicate that the (In0.94−x,Gax,Fe0.06)Sb layers have a zinc blende crystal structure without any other second phase. The lattice constant of the (In0.94−x,Gax,Fe0.06)Sb films changes linearly with the Ga concentration x, indicating that Ga atoms substitute In atoms in the zinc-blende structure. We found that the carrier type of (In0.94−x,Gax,Fe0.06)Sb can be systematically controlled by varying x, being n-type when x ≤ 10% and p-type when x ≥ 20%. Characterization studies using magnetic circular dichroism spectroscopy indicate that the (In0.94−x,Gax,Fe0.06)Sb layers have intrinsic ferromagnetism with relatively high Curie temperatures (TC = 40–120 K). The ability to widely control the fundamental material properties (lattice constant, bandgap, carrier type, and magnetic property) of (In0.94−x,Gax,Fe0.06)Sb demonstrated in this work is essential for spintronic device applications. [ABSTRACT FROM AUTHOR]

We demonstrate spin-valve magnetoresistance (MR) with a current-in-plane (CIP) configuration in (Ga,Fe)Sb/InAs (thickness tInAs nm)/(Ga,Fe)Sb trilayer heterostructures, where (Ga,Fe)Sb is a ferromagnetic semiconductor (FMS) with high Curie temperature (TC). An MR curve with an open minor loop is clearly observed at 3.7 K in a sample with tInAs = 3 nm, which originates from the parallel-antiparallel magnetization switching of the (Ga,Fe)Sb layers and spin-dependent scattering at the (Ga,Fe)Sb/InAs interfaces. The MR ratio increases (from 0.03 to 1.6%) with decreasing tInAs (from 9 to 3 nm) due to the enhancement of the interface scattering. This demonstration of the spin-valve effect in Fe-doped FMS heterostructures paves the way for device applications of the high-TC FMS. [ABSTRACT FROM AUTHOR]