Structural and optical properties of arsenic-oxide microcrystals on GaAs substrate for photonic applications

Abstract

Nano and microstructure semiconductor heterostructures are employed for a wide variety of sensor and photonics applications. The present paper discusses the synthesis of arsenic-oxide microcrystals by using electroless chemical etching of GaAs (100) substrate surface using aqueous nitric acid for 1–5 min at room temperature. The structural and morphological analyses reveal that the density of the polycrystalline octahedron microcrystals (15–20 μm size) of arsenic-oxide increased with the etching duration. The sample surfaces are engulfed by the arsenic-oxide microcrystals after 2 min of etching. The chemical analysis of the samples established the arsenic-oxide phases formed due to the surface oxidation during the etching process. The samples showed no distinctive Ga3d chemical state etched for more than 2 min. The crystallite size (55.70–86.68 nm), strain (2.93–13.7 × 10−4), and dislocation density (1.331– 3.22 × 1010 cm−2) in the microcrystals are estimated from the x-ray diffraction analysis. The Raman spectra of the micro-crystalline arsenic-oxides showed a 6-7 cm−1 red shift from its respective reference peak due to the presence of tensile residual stress. The samples exhibited photoluminescence (PL) in the UV and blue wavelength ranges due to the near band-edge transition (298.5 nm) in the arsenic-oxide microcrystals and defects transitions (310 nm, 405 nm, 430 nm) in oxide species. The peak intensity of the broad blue emission increases with the etching time. The time-resolved PL (TRPL) results showed the exciton average lifetime of the crystals is less than 1 ns which predicts their possible use in fast optical sensing, flashes, and fast switching applications.