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Characterization of epiready n+-GaAs (100) surfaces by SPV-transient
Author(s): Juha Sinkkonen; Sergey Novikov; Aapo Varpula; J. Haapamaa
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Paper Abstract

Surface photovoltage (SPV) transient provides a non-destructive, contact-free method for characterization of semiconductor surfaces. Here we study SPV-transients of differently cleaned, heavily doped epiready GaAs wafers. After a rapid initial part the transient shows a very slow decay taking place in 100 - 1000 s time scale. Chemical NH4OH:H2O2:H2O cleaning and atomic hydrogen UHV cleaning are applied. SPV-transients are measured by Kelvin probe in normal atmospheric conditions. A large signal surface trapping model is developed which includes both majority and minority carrier processes and covers the whole light on, steady state, light off sequence. Model fitting allows band bending, energy and density of surface states as well as electron and hole capture cross-sections to be extracted. The results show that the traps are electronic states in thin oxide layer covering the samples. This conclusion is based on the finding that the capture cross-sections are very small, in the range 10-19 - 10-26 cm2, which calls tunneling for explanation. This indicates that after cleaning the oxide layer is rapidly re-grown in laboratory atmosphere in less than 30 min. Typical band bendings are 0.6 - 0.8 eV, trap energies are slightly above the mid-gap and the density of occupied trap states is around 5×1012 cm-2 at thermal equilibrium.

Paper Details

Date Published: 9 January 2008
PDF: 10 pages
Proc. SPIE 6800, Device and Process Technologies for Microelectronics, MEMS, Photonics, and Nanotechnology IV, 68001D (9 January 2008); doi: 10.1117/12.759378
Show Author Affiliations
Juha Sinkkonen, Helsinki Univ. of Technology (Finland)
Sergey Novikov, Helsinki Univ. of Technology (Finland)
Aapo Varpula, Helsinki Univ. of Technology (Finland)
J. Haapamaa, Coherent Finland Oy (Finland)

Published in SPIE Proceedings Vol. 6800:
Device and Process Technologies for Microelectronics, MEMS, Photonics, and Nanotechnology IV
Hark Hoe Tan; Jung-Chih Chiao; Lorenzo Faraone; Chennupati Jagadish; Jim Williams; Alan R. Wilson, Editor(s)

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