# Assessment of Optical and Phonon Characteristics in MOCVD-Grown (AlxGa1−x)0.5In0.5P/n+-GaAs Epifilms

## TL;DR

This paper studies the optical and phonon properties of a quaternary alloy grown on GaAs to improve photonics devices like LEDs and photodetectors.

## Contribution

The study provides new insights into the energy-dependent characteristics of (AlxGa1−x)0.5In0.5P/n+-GaAs epilayers using multiple analytical techniques.

## Key findings

- Raman scattering and FTIR results revealed phonon behavior in the FIR region.
- Optical constants validated TD-PL measurements of bandgap energies in the NIR to UV range.
- Macroscopic models effectively analyzed the energy-dependent optical and vibrational properties.

## Abstract

Quaternary (AlxGa1−x)yIn1−yP alloys grown on GaAs substrates have recently gained considerable interest in photonics for improving visible light-emitting diodes, laser diodes, and photodetectors. With two degrees of freedom (x, y) and keeping growth on a lattice-matched GaAs substrate, the (AlxGa1−x)0.5In0.5P alloys are used for tuning structural, phonon, and optical characteristics in different energy regions from far-infrared (FIR) → near-infrared (NIR) → ultraviolet (UV). Despite the successful growth of (AlxGa1−x)0.5In0.5P/n+-GaAs epilayers, limited optical, phonon, and structural characteristics exist. Here, we report our results of carefully examined optical and vibrational properties on highly disordered alloys using temperature-dependent photoluminescence (TD-PL), Raman scattering spectroscopy (RSS), and Fourier-transform infrared reflectivity (FTIR). Macroscopic models were meticulously employed to analyze the TD-PL, RSS, and FTIR data of the (Al0.24Ga0.76)0.5In0.5P/n+-GaAs epilayers to comprehend the energy-dependent characteristics. The Raman scattering and FTIR results of phonons helped analyze the reflectivity spectra in the FIR region. Optical constants were carefully integrated in the transfer matrix method for evaluating the reflectivity R(E) and transmission T(E) spectra in the NIR → UV regions, validating the TD-PL measurements of bandgap energies (EgPL).