Exploring the Optical and Magnetic Properties of Molecular Beam Epitaxy-Grown Diluted Multicomponent III-V Semiconductor Nanofilms

Dilute multicomponent semiconductors represent a class of alloys that integrate semiconducting properties with ferromagnetism or superconductivity. This combination of electronic and ferromagnetic or superconducting properties yields novel physical characteristics that are intriguing for both fundamental research and practical device applications. Tailoring the band structure through the introduction of additional doping ions such as P, In, or Bi in the III-V semiconductor matrix [1–3] enables the exploration of innovative device concepts.

For this study, we present a comprehensive investigation into the relevant physical properties of dilute multicomponent III-V semiconductor nanofilms. This investigation employs a combination of analytical techniques including Fourier-transform infrared spectroscopy, spectroscopic ellipsometry (SE), high-resolution X-ray diffraction (HRXRD), micro-Raman spectroscopy, SQUID magnetometry, and broadband ferromagnetic resonance spectroscopy (VNA-FMR).

This multifaceted approach allows for the determination of key magnetic and optical characteristics of the material, such as dielectric functions, band structure, Curie temperature, saturation magnetization (M_s), anisotropy fields (crystallographic cubic Hc and uniaxial H_u), axes and planes of easy magnetization, ferromagnetic resonance line width (ΔH), Gilbert damping constant (α), and more. A thorough understanding of the magnetic characteristics of the samples facilitates the realization of the full potential of ultra-thin III-Mn-V semiconductors and topological semimetals for applications in magnetic storage and microwave technologies [4,5].

Specifically, our focus lies on quaternary (Ga,Mn)(P,As) compounds with varying P (up to 32%) and Mn (up to 8%) content, as well as SnInTe with different In (up to 30%) content epitaxial layers grown by molecular beam epitaxy (MBE) on p-type and semi-insulating (001) GaAs substrates. The absorption infrared spectrum was measured using a Nicolet 380 spectrometer (Thermo Fisher Scientific), collecting high-resolution spectral data over a wide range from 400 to 4000 cm^-1. These measurements were complemented by SE-2000 Semilab multi-angle spectroscopic ellipsometer readings (working wavelength range: 250 nm to 2100 nm).

Additionally, the crystalline quality of the layers and sharp interfaces with the substrate were confirmed using HRXRD, revealing the pseudomorphic growth of very thin nanofilms on (001) GaAs. Composition analysis of the thin films was conducted using secondary-ion mass spectrometry (SIMS) and Auger electron spectroscopy (AES).

Micro-Raman spectroscopy was employed to estimate the free hole densities in the nanolayers. By combining the aforementioned experimental methods, we could precisely define the band structures of the epitaxial layers and identify additional impurity states within the band gaps.