Recombination at Dislocations in Silicon and Gallium Arsenide
For many years it has been known that dislocations in semiconductors are associated with energy levels within the band gap. Such levels have been detected experimentally in many ways. For example charge trapped at the dislocation level both alters the free carrier concentration which can be measured using the Hall effect and also introduces unpaired electrons whose spin can be detected using EPR. The thermal capture and re-emission of carriers at the defect energy levels can be measured using DLTS. The emission of photons when carriers make a transition to the dislocation level can be observed in photoluminescence experiments. In each case the experimental results obtained can be directly related to the position or concentration of the energy levels present, or the relevant theory describing the experiment is sufficiently complete that the data may be interpreted in such terms with a good degree of confidence1. In respect to deformation induced dislocations in silicon, all of the above techniques have been widely used to characterise the parameters describing energy levels at dislocations. It is thus surprising that the cause of the energy levels is still not understood. They have been variously attributed to the dislocation strain field, dangling bonds at the dislocation core, kinks, jogs, faults in the reconstruction process of dangling bonds, and impurities or point defect centres present at the dislocation.
KeywordsScrew Dislocation Minority Carrier Space Charge Region Hole Capture Electron Capture Rate
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