Optical absorption of composition-tunable InGaAs nanowire arrays

Area of Science:

• Materials Science
• Nanotechnology
• Optoelectronics

Background:

• Indium Gallium Arsenide (InGaAs) nanowire (NW) arrays are promising for photovoltaics and photodetectors due to their electronic properties and tunable band gaps.
• Understanding their optical absorption is crucial for optimizing device performance.

Purpose of the Study:

• To systematically investigate the optical absorption characteristics of composition-tunable vertical InGaAs NW arrays.
• To determine the influence of composition (Ga-molar fraction) and geometry (diameter, period, fill factor) on optical generation rate and absorption spectra.

Main Methods:

• Finite-difference time-domain (FDTD) simulations were used to model optical generation rates.
• Spectrally resolved ultraviolet-visible-near-infrared (UV-vis-NIR) spectroscopy was employed to measure optical absorption on transferred NW arrays.

Main Results:

• Simulations showed InGaAs NWs with diameters of 100-250 nm and moderate fill factors enhance generation rates compared to bulk materials.
• Increased Ga-molar fraction requires adjusted geometry (smaller fill factors, larger diameters) to maintain high generation rates.
• Experimental results indicated that NW diameter variations (< ±20 nm) strongly affect absorption spectra, causing shifts > 700 meV, while composition changes (0 < x(Ga) < 0.5) had negligible influence.

Conclusions:

• Optical absorption in InGaAs NW arrays is significantly more sensitive to geometric parameters than to electronic band gap variations.
• Precise control over NW diameter is critical for tuning optical absorption in InGaAs NW-based devices.