Laser Assisted Surface Photovoltage Spectroscopy: A New Tool for an Accurate Determination of the Bandgap of Semiconductor Epitaxial Layers
A new technique is presented for an accurate determination of the bandgap of semiconductor bulk and quantum structures under the strong influence of localized states. It is based on a pump-probe configuration where an additional sub bandgap cw pump laser beam is used in a conventional chopped light geometry surface photovoltage spectroscopy setup. The main role of pump beam is limited to saturate the sub bandgap localized states whose contribution otherwise swamp the information related to the bandgap of material. The pump beam is found to be very effective in suppressing the effect of surface/interface and bulk trap states.
KeywordsSPV Pump-probe measurement GaAs
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Authors acknowledge Dr. V. K. Dixit, Dr. S. D. Singh, Mr. Shailesh Khamari for useful discussions and thank Mr. U. K. Ghosh and Mr. A. Khakha for their help during the growth of the samples. Authors also acknowledge Dr. P. D. Gupta, Director RRCAT for his constant support during the course of this work.
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