Observation of Very Deep Levels by Optical DLTS
Current transient spectroscopy (OTCS) is known to be able to give the electrical characteristics of the traps in semi-insulating material, as classic DLTS is in n- or p-type semiconductors. The method is limited by difficulties occurring for very deep traps. We explain here the difficulties — mainly the occurrence of negative transients — and set up an experimental procedure to interpret the data. Our first results show that, in Bridgman GaAs:Cr, the HL1 and EL2 levels are not the only levels that are present. At comparable concentration, the HL1 trap can be detected but the EL2 trap cannot.
KeywordsDeep Level Arrhenius Plot Negative Peak Current Transient Deep Trap
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