Method for Improving the Quality of Porous Gallium Arsenide Wafer for Anti-Reflecting Coating of Solar Cells

The authors proposed a way to increase the efficiency of solar cells based on gallium arsenide. The method is based on the formation of a porous layer on the surface of the solar cell to create an anti-reflective effect. The paper examines the influence of such parameters of the porous layer as the uniformity and size of the crystallites on the percentage of light reflection. A method of forming a porous wafer by anodizing with a pulsed current is proposed, the duty cycle of which consists of the time of turning on the current and the time of turning it off. During experimental studies, it was established that the structure of the layer depends mainly on the time of turning on the anodizing current during the work cycle. Pulse anodizing creates a bimodal effect in the crystal size distribution. The paper presents the photoluminescence spectra of samples obtained both during anodization with pulsed current and during anodization with direct current. The dependence of the percentage of light reflection on the parameters of the porous wafer was investigated. It is shown that the reflection is affected by the uniformity of the wafer and the size of the crystallites. The lowest percentage of reflection, which is equal to 4% at a light wavelength of 550 nm, was obtained with the following parameters of an anodizing pulse current: an anodizing current on time of 100 ms, and a current off time of 40 ms.