Effect of substrate quality on GaAs solar cell performances

A study was made of the effect of substrate quality on the properties of GaAs/GaAlAs heterophase solar cells grown by liquid-phase epitaxy and optimized for space application. Extensive statistics were obtained by evaluating the performances of about one thousand 2*2 cm/sup 2/ GaAs solar cells. The effects of the following substrate parameters were evaluated: dislocation density, carrier concentration, growth technique, kind of dopant, and manufacturer. It is shown that cell efficiency is strictly related to the substrate carrier concentration and minority carrier diffusion length. Cell efficiencies of 17% AM0 can be routinely achieved using the substrate as an active part of the device. No direct correlation is observed between cell efficiency and dislocation density up to 20000 defects/cm/sup 2/.<>