Defect Specific Photoconductance (DSPC)© technology differentiates between point and extended defects based on their recombination characteristics: J. Appl. Phys. 112, 063715 (2012).#  

Point defects, which dominate the bulk of the semiconductors, can be due to impurities and crystal defects. Extended defects include crystal imperfections, such as:
  • Surface and interfaces
  • Grain boundaries
  • Dislocations
  • Clusters of impurities of crystal defects
  • Homo- and hetero-junctions

DSPC offers several modes of operation, allowing for characterization of different sets of material parameters including surface and bulk electrical properties. Selection of most appropriate modality depends on type of the device (PV, HB-LED, IC, RadDetectors) and on the material (e.g., Si, CdTe, CdZnTe, GaN, GaAs, etc.).


Measurement Capability in Si


Bulk
Minority carrier recombination lifetime (no surface treatment required)
Effective carrier generation rate in the bulk
Effective carrier injection level
Doping concentration

Surface
Surface recombination time constant
Surface capture velocity
Surface state density
Surface charge
Effective carrier generation rate in the surface region




DSPC ANALYZER

DSPC
©
  Analyzer additionally to a new analysis method offers non-contact material characterization capable to distinguish between bulk and surface characteristics as well as bulk point defects and bulk extended crystal imperfections such as grain boundaries, dislocation conglomerates or clusters of point defects. The DSPC Analyzer covers resistivity range spanning more than 10 orders of magnitude from 1 ohm-cm to 1010 ohm-cm. 

STAND-ALONE ADVANCED DSPC ANALYSIS SOFTWARE

DSPC analysis offers a new approach to characterization of semiconductors based on the well known free carrier absorption or photoconductance phenomena. The measurement techniques may utilize RF, microwaves, and contact techniques. Stand-alone DSPC
©
 Analysis software does not typically require any hardware modifications, however it may require critical modifications of the measurement procedures that are guided by the DSPC© Analyzer software.


BASIC PRINCIPLES

 At low carrier injection levels, carrier recombination through extended defects is controlled by the electrostatic potential barrier formed at the defects. The photoconductance associated with recombination through extended defects under depletion conditions exhibits characteristic logarithmic decay after cessation of illumination, unlike recombination through point defects in the bulk, which is characterized by the exponential decay of the photoconductance.
 
Differentiation between time dependence of the photoconductance decay associated with recombination through the point defects and through the extended crystal imperfections is used as a basis of the DSPC methodology.
 
DSPC allows for the separation of the bulk and surface characteristics without any additional surface treatments, enabling electrical characterization of both bulk and thin-film wafer structures in a number of semiconductor applications.


#Copyright (2012) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.