Sorption-Induced Conductivity Changes in Compound Semiconductors.
Technical rept., Sep 69-Jun 71,
PRINCETON UNIV N J DEPT OF ELECTRICAL ENGINEERING
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Large changes in the equilibrium semiconductivity of thin compound semiconductors induced by chemisorption are investigated. Evaporated films and single crystals of CdS and single crystals of CdSe both n-type show a gradual reduction in semiconductivity coupled with an increase in activation energy with increasing oxygen pressure above a certain threshold. Evaporated CdS films are more sensitive to such changes at lower pressure as are the more highly compensated Cu and Au doped films. Oxygen chemisorption states of CdS and CdSe are distributed in energy in the semiconductor bandgap being largest at the conduction band edge and decreasing exponentially with energy into the gap. Atomically structured CdS single crystal surfaces, obtained by ion bombardment and vacuum annealing are insensitive to chemisorption. Thus, adsorption sites can be associated with surface impurities andor imperfections. PbI2 p-type exhibits an increase in semiconductivity with oxygen pressure in accord with the models developed in the report. Author
- Physical Chemistry
- Solid State Physics