WHAT INFORMATION ON EXTENDED DEFECTS DO WE OBTAIN FROM BEAM-INJECTION METHODS

A review is given of the problems and results of the application of beam injection methods to extended defects (dislocations and grain boundaries) in silicon. Some conditions for reliable work are mentioned. Recent work shows that there are two types (classes) of response of the electron-beam-induced current (EBIC) contrast to variation in temperature and to injection level; the first can be explained as due to charge-controlled recombination at deep traps, and the second is probably caused by shallow centres which reduce the minority-carrier lifetime. The recombination activity of dislocations is related to the decoration by impurity atoms. A new technique for investigating grain boundaries (GBs) is given; charged GBs separate electrons from holes and generate a recombination current. This GB EBIC depends on the distance of the beam from the GB. On application of a small bias the barrier height and its sensitivity to the injection can be measured locally. The trap states in the GB are revealed by measuring the transverse conductance across the GB under the influence of a focused beam of monochromatic subband gap light (GB photoconductance spectroscopy).