INVESTIGATION OF THE PROCESSES OF ELECTRON INJECTION DURING DISSOLUTION OF P-SI IN ACIDIC FLUORIDE AND ALKALINE MEDIA

The phenomena of electron injection occurring during anodic dissolutio n of Si are studied in a dual-electrolyte transistor-like geometry: va riations in the population of minority carriers of a p-Si wafer result ing from injection are detected by a second liquid junction on the bac k side of the electrode. Investigations in acidic fluoride media show that electrons injected during porous silicon formation undergo ready surface recombination. A significant back current is detected in the e lectropolishing regime, indicating that important injection processes occur even under the latter conditions. Analogous investigations at p- Si in 2 M KOH show electron injection in correspondence to the oxidati on peak leading to passivation. Results are compared with literature d ata and discussed with reference to current models of silicon dissolut ion.