Doping Dependent Magnetic Behavior in MBE Grown GaAs1-xSbx Nanowires

Raj Kumar,Jia Li,Lewis Reynolds,Shanthi Iyer,Yang Liu

doi:10.1038/s41598-020-65805-4

Abstract

Intrinsic and Te-doped GaAsSb nanowires with diameters ~100–120 nm were grown on a p-type Si(111) substrate by molecular beam epitaxy (MBE). Detailed magnetic, current/voltage and low-energy electron energy loss spectroscopy measurements were performed to investigate the effect of Te-doping. While intrinsic nanowires are diamagnetic over the temperature range 5–300 K, the Te-doped nanowires exhibit ferromagnetic behavior with the easy axis of magnetism perpendicular to the longitudinal axis of the nanowire. The temperature dependence of coercivity was analyzed and shown to be in agreement with a thermal activation model from 50–350 K but reveal more complex behavior in the low temperature regime. The EELS data show that Te doping introduced a high density of states (DOS) in the nanowire above the Fermi level in close proximity to the conduction band. The plausible origin of ferromagnetism in these Te-doped GaAsSb nanowires is discussed on the basis of d0 ferromagnetism, spin ordering of the Te dopants and the surface-state-induced magnetic ordering.

Highlights

It has been nearly six decades since Wagner and Ellis[1] reported the growth of Si whiskers via the vapor-liquid-solid (VLS) mechanism, which led to the extensive pursuit of research on semiconductor nanowires
The presence of the 1.8 eV peak in the energy loss spectroscopic (EELS) spectra of the Te-doped nanowires but not in the intrinsic ones strongly suggests that doping creates levels in the band structure, which most likely provides some insight on our observation of ferromagnetic behavior and the associated anisotropic magnetic properties of the doped nanowires compared to their lack in the intrinsic ones
Our data reveal ferromagnetic behavior when the applied field is oriented perpendicular to the longitudinal axis of the nanowires for doped nanowires but diamagnetic for intrinsic GaAsSb

Summary

Introduction

It has been nearly six decades since Wagner and Ellis[1] reported the growth of Si whiskers via the vapor-liquid-solid (VLS) mechanism, which led to the extensive pursuit of research on semiconductor nanowires (see, for example, the perspective by Yang, et al.[2] and the reviews in refs. 3–5). The intrinsic GaAs1-xSbx nanowires exhibit clear diamagnetic behavior at room temperature and 5 K while the Te-doped nanowires show strong ferromagnetic behavior with a saturation magnetization of ~3 emu/ cm[3], as shown, respectively.

Results

Conclusion