We report on photoassisted wet chemical formation of thin oxide films on n-GaN layers in potassium hydroxide based electrolytes at room temperature. The kinetics of the oxide formation and dissolution were examined via photocurrent transients. The tendency of the photocurrent to level out during photoelectrochemical etching experiments is associated with a quasiequilibrium state at the semiconductor/electrolyte interface. Homogeneous oxide films were grown in weak alkaline solutions (11<pH<13) under potentionstatic control with oxidation rates of up to 250 nm/h and characterized by Auger electron spectroscopy. Consequences on wet photochemical etch strategies are discussed.
We report the structural properties of InGaN/GaN/AlGaN multiple quantum wells (MQWs) by means of two-dimensional reciprocal space mapping (RSM) of high resolution x-ray diffraction. The influence of Si doping in GaN barriers on the characteristics has been studied for 12-period MQWs grown by metalorganic chemical vapor deposition, which have different Si doping concentrations in the GaN barriers ranging from 1×1017 to 3×1019 cm−3. Information on the structural quality of these MQWs was extracted from the linewidth broadening of the higher-order superlattice satellite peaks, as well as from the presence of Pendellösung oscillations. The measured diffraction curves were modeled using kinematic diffraction theory. From the symmetric and asymmetric RSMs around (0002), (0004) and (112̄4) reflections, we found that the InGaN/GaN/AlGaN MQWs are grown coherently on the GaN base layer. Better interface properties are achieved with Si doping. Our results indicate that Si doping in the GaN barriers affects the interface quality of the InGaN/GaN MQW systems, and thus, also influences the optical properties.
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