TRANSPORT OF PHOTOGENERATED CHARGE-CARRIERS THROUGH CRYSTALLINE GAP NETWORKS INVESTIGATED BY INTENSITY-MODULATED PHOTOCURRENT SPECTROSCOPY

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