Photoluminescence of n-type CdGeAs₂

Area of Science:

• Semiconductor physics
• Materials science
• Solid-state chemistry

Background:

• Cadmium germanium arsenide (CdGeAs2) is a ternary semiconductor with potential applications.
• Understanding doping effects is crucial for tailoring semiconductor properties.
• Photoluminescence (PL) is a key technique for probing electronic transitions and defects.

Purpose of the Study:

• To investigate the impact of intentional doping (Indium, Selenium, Tellurium) on n-type CdGeAs2.
• To analyze photoluminescence spectra and correlate them with carrier concentration and doping levels.
• To identify dominant recombination mechanisms and acceptor levels in doped CdGeAs2.

Main Methods:

• Synthesis of n-type CdGeAs2 samples via intentional doping.
• Photoluminescence (PL) spectroscopy at various doping concentrations.
• Analysis of PL peak shifts and broadening in relation to electron concentration.
• Comparison of experimental data with theoretical models for recombination processes.

Main Results:

• A near-edge PL band in heavily In-doped CdGeAs2 shifts to higher energy and broadens with increased electron concentration.
• Free-to-bound transitions involving a shallow 120 meV acceptor level dominate at high doping (>2 × 10^18 cm^-3).
• A lower energy PL band, attributed to deep acceptors, is observed in lightly doped n-type samples (Indium, Selenium, Tellurium) and p-type samples, but absent in heavily In-doped samples.

Conclusions:

• The observed PL behavior in doped CdGeAs2 is explained by donor-acceptor pair, free-to-bound transitions, band filling, tailing, and band gap shrinkage.
• The disappearance of the deep acceptor PL band in heavily Indium-doped CdGeAs2 suggests it may be related to Cadmium vacancies.
• Doping significantly influences the electronic properties and defect landscape of CdGeAs2.