Transport of photogenerated charge carriers through crystalline GaP networks investigated by intensity modulated photocurrent spectroscopy

The transport of photogenerated electrons through porous n-GaP electrodes has been investigated with Intensity Modulated Photocurrent Spectroscopy. Porous layers with a thickness of between 1 and 200 mu m were formed on GaP substrates by anodic etching of crystalline n-GaP electrodes. They consist of a network of crystalline GaP interpenetrated with the electrolyte It is shown that the transit time of photogenerated electrons through the depleted porous network is larger than the RC response time. Hence, IMPS performed in the frequency window below (RC)(-1) directly probes the transient photocurrent flow in the depleted porous network. The relatively long transit times observed with IMPS are attributed to strongly meandering paths of the photogenerated electrons through the crystalline network, probably determined by the potential distribution in the depleted network.