Bruce J. Tufts

Fabrication of minority‐carrier‐limited n‐Si/insulator/metal diodes

A photoelectrochemical anodization technique has been used to fabricate n-Si/insulator/metal (MIS) diodes with improved electrical properties. MIS structures fabricated with Au have provided the first experimental observation of a solid-state n-Si surface barrier device whose open circuit voltage Voc is controlled by minority-carrier bulk diffusion/recombination processes. For these diodes, variation of the minority-carrier diffusion length and majority-carrier dopant density produced changes in Voc that were in accord with bulk diffusion/recombination theory. Additionally, the variation in Voc in response to changes in the work function of the metal overlayer indicated that these MIS devices were not subject to the Fermi level pinning restrictions observed for n-Si Schottky structures. X-ray photoelectron spectroscopic characterization of the anodically grown insulator indicated 8.2±0.9 A of a strained SiO2 layer as the interfacial insulator resulting from the photoanodization process.

Correlations between the interfacial chemistry and current-voltage behavior of n-GaAs/liquid junctions

Correlations between the surface chemistry of etched, (100) oriented n-GaAs electrodes and their subsequent photoelectrochemical behavior have been probed by high-resolution x-ray photoelectron spectroscopy. GaAs photoanodes were chemically treated to prepare either an oxide-free near stoichiometric surface, a surface enriched in zero-valent arsenic (As0), or a substrate-oxide terminated surface. The current-voltage (I-V) behavior of each surface type was subsequently monitored in contact with several electrolytes.