Controlled electrochemical growth of micro-scaled As2O3 and Ga2O3 oxide structures on p-type gallium arsenide

In this work, the double cell electrochemical etching technique is employed to study the evolution of surface morphology during the etching of p-type gallium arsenide (GaAs) in a HF:C2H5OH electrolyte solution. It is observed that arsenic trioxide (As2O3) and gallium oxide (Ga2O3) micron-sized transparent oxide structures grow on the GaAs surface under certain etching conditions. At a large enough current density, a continuous array of As2O3 microcrystals on GaAs substrate is formed. On the other hand, prolonged etching time enables formation of an oxide layer with drastically enhanced content of the Ga2O3 phase which is known to be a good dielectric with a wide band gap. The chemical and morphological variation from microcrystals to micro-rods is explained in terms of anodic dissolution and the oxidation process of GaAs substrates. The formed oxide species on GaAs surface can provide a good opportunity to create oxide/GaAs hetero-structures with heterojunctions for optoelectronic applications. The visible range photoluminescence (PL) properties of these micro-structures are also investigated. As2O3 and Ga2O3 micro-structures have strong PL peaks at 520 and 480 nm, respectively. Finally, the recombination lifetimes of the charge transitions are examined and discussed in the context of the underlying recombination mechanisms. These results could initiate new perspectives for As2O3 and Ga2O3 micro-structures to be employed in high-performance optoelectronic devices.