Kumar, Amit (1992) Charge transfer studies of semiconductor interfaces. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:08252011-134056337
For all semiconductors (n-Si, p-Si, n-GaAs, n-InP, a-Si:H), the spectral response of liquids junctions, in the short wavelength region (200-600 nm), showed higher quantum yields than metal junctions. This general trend was independent of redox species, solvent, supporting electrolyte, and metal overlayer. This technique was also used to distinguish between Schottky barrier behavior from electrocatalytic behavior of metal overlayers. Studies of n-Si photoelectrodes in aqueous and non-aqueous electrolytes have been conducted. For all n-Si/CH_3OH-dimethylferrocne^(+/O)(Me_2Fc^(+/O)) cells, the forward bias dark currents,the open circuit voltage (V_(oc)), and temperature dependence of V_(oc) were independent redox species concentrations. All n-Si photoanodes (naked and coated with discontinuous metal overlayers) were found to be unstable in aqueous electrolytes. Novel metal/insulator/semiconductor devices have been fabricated through the anodic growth of the insulator layer in a methanol based electrolyte. These devices do not suffer from Fermi level pining restrictions, and some exhibit electronic properties limited by minority carrier transport. A theoretical framework has been formulated to describe the behavior of photoelectrolysis cells, and experiments at n-SrTiO3/5.0 M KOH(aq)/Pt junctions have been conducted. The data exhibits a photocurrent threshold in the short circuit electrolysis current at 0.02-0.03 mW/cm^2 of 325 nm illumination, which is consistent with the theoretical framework. The behavior of Si/CH_3OH-Me_2Fc^(+/O) junctions has been investigated under high injection conditions. With a structure having n+ diffused back contacts, V_(oc)s of 626+5 mV were obtained at short circuit photocurrent densities of 20 mA/cm^2. The diode quality factor and reverse saturation current were 1.8+0.1 and (2.6+1.5)x 10^(-8) A/cm^2, respectively. These data are consistent with recombination dominated by the base and back contact regions, and not at the Si/CH_3OH interface.
|Item Type:||Thesis (Dissertation (Ph.D.))|
|Degree Grantor:||California Institute of Technology|
|Division:||Chemistry and Chemical Engineering|
|Thesis Availability:||Restricted to Caltech community only|
|Defense Date:||16 September 1991|
|Default Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||26 Aug 2011 18:18|
|Last Modified:||26 Dec 2012 04:38|
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