The preparation and properties of thin polycrystalline GaAs solar cells with grain boundary edge passivation

This paper describes the preparation and properties of thin-film (9-µm) polycrystalline GaAs solar cells, fabricated on molybdenum substrates by the metalorganic process. These cells, of a Schottky structure, have an efficiency of 5.7 percent under simulated AM1 conditions, with no antireflective (AR) coating. This is achieved by passivating the grain boundary edges, resulting in a reduction of shunt leakage by five to six decades. The effect of treatments on the resulting electrical properties is described; both treatments during fabrication as well as on complete devices are considered here. These include a critic acid etch treatment prior to anodization, and hydrochloric acid treatments on completed devices. The effect of annealing is also described briefly together with techniques by which full recovery of cell performance can be achieved. Finally, transport properties are outlined briefly in order to highlight the primary current transport mechanisms in these cells.