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Title: Pump-probe surface photovoltage spectroscopy measurements on semiconductor epitaxial layers

Pump-probe Surface Photovoltage Spectroscopy (SPS) measurements are performed on semiconductor epitaxial layers. Here, an additional sub-bandgap cw pump laser beam is used in a conventional chopped light geometry SPS setup under the pump-probe configuration. The main role of pump laser beam is to saturate the sub-bandgap localized states whose contribution otherwise swamp the information related to the bandgap of material. It also affects the magnitude of Dember voltage in case of semi-insulating (SI) semiconductor substrates. Pump-probe SPS technique enables an accurate determination of the bandgap of semiconductor epitaxial layers even under the strong influence of localized sub-bandgap states. The pump beam is found to be very effective in suppressing the effect of surface/interface and bulk trap states. The overall magnitude of SPV signal is decided by the dependence of charge separation mechanisms on the intensity of the pump beam. On the contrary, an above bandgap cw pump laser can be used to distinguish the signatures of sub-bandgap states by suppressing the band edge related feature. Usefulness of the pump-probe SPS technique is established by unambiguously determining the bandgap of p-GaAs epitaxial layers grown on SI-GaAs substrates, SI-InP wafers, and p-GaN epilayers grown on Sapphire substrates.
Authors:
; ; ;  [1] ;  [2]
  1. Semiconductor Physics and Devices Lab., Raja Ramanna Centre for Advanced Technology, Indore-452013, M. P. (India)
  2. Indus Synchrotrons Utilization Division, Raja Ramanna Centre for Advanced Technology, Indore-452013, M. P. (India)
Publication Date:
OSTI Identifier:
22254904
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 85; Journal Issue: 4; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; BEAMS; EPITAXY; GALLIUM ARSENIDES; GALLIUM NITRIDES; GEOMETRY; LASERS; LAYERS; PROBES; SAPPHIRE; SEMICONDUCTOR MATERIALS; SPECTROSCOPY; SUBSTRATES