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High temperature deformation of silicon

Technical Report ·
OSTI ID:6003590

This work is concerned with characterizing, observing, and exploring the origins of a silicon crystalline defect's electrical properties. These goals are accomplished by unique applications of the electron-beam-induced current (EBIC) technique. Bulk silicon solar cell properties are correlated with EBIC at low accelerating voltage (LAV-EBIC) and high accelerating voltage (HAV-EBIC). HAV-EBIC currents were related linearly to the short-circuit current density, conversion efficiency, and dislocation density, but LAV-EBIC currents were found to be independent of the same properties. The difference in probing depth was used to explain the discrepancy. EBIC and transmission electron microscopy (TEM) were combined into one scanning transmission electron microscope (STEM) to unambiguously correlate electrical activity with defect structure. This technique is successfully applied to defects in polycrystalline silicon, but the complexity and variety of general silicon defects made this approach unsuitable for uncovering the origins of a defect's electrical activity. These origins were investigated by welding together two float-zone silicon wafers to form twist boundaries. These boundaries are composed of a square array of screw dislocations of sufficient number and purity to separate impurity effects from the intrinsic electrical activity. Applying the Kittler and Seifert model, the silicon screw dislocations were estimated to have between 0.3 and 0.5 recombination sites per Burgers vector. It was subsequently concluded that kinks and jogs were responsible for screw dislocation electrical recombination. 82 refs., 23 figs.

Research Organization:
Sandia National Labs., Albuquerque, NM (USA); Cornell Univ., Ithaca, NY (USA)
Sponsoring Organization:
NSF
DOE Contract Number:
AC04-76DP00789
OSTI ID:
6003590
Report Number(s):
SAND-90-7035; ON: DE91009102; CNN: ECS8619049
Country of Publication:
United States
Language:
English