Material mechanics of GaAs1-xPx alloy epilayers for optical frequency conversion in the mid-infrared

We report nanoindentation measurements of Hydride Vapor Phase Epitaxy grown GaAs_1-xP_x epilayers, demonstrating a linear trend in Young's modulus with increasing phosphorus content. The corresponding hardness trend shows significant bowing with a peak of 10.7GPa occurring near 80% P-content. Some epilayers exhibit non-negligible spatial variation in their mechanical properties, which is investigated with complementary measurements. Photoluminescence measurements indicate high composition uniformity, while atomic force microscopy reveals a direct correlation between surface roughness and mechanical variability. Preliminary laser-induced damage threshold results are reported, and the implications for material optimization are discussed. With a 1070-nm continuous wave pump laser, GaAs_0.75P_0.25 and GaAs_0.52P_0.48 epilayers demonstrated thresholds of 600kW/cm² and 300kW/cm², respectively. This work supports the development of practical laser sources in the mid-infrared spectral region for applications such as remote sensing, IR countermeasures, and spectroscopy.