Evaluation of a defect capture cross section for minority carriers: Application to GaAs

Abstract

The majority-carrier trapping cross section for a majority-carrier trap can be obtained using capacitance spectroscopy by monitoring the kinetics of trap filling. This method cannot be applied for the determination of the trapping cross section of minority carrier by this majority-carrier trap because the capture or emission kinetics cannot be observed. Here we propose a method to measure the minority-carrier trapping cross section for majority-carrier trap. It is not a general method but limited to defects which have the property to anneal under minority-carrier injection, a rather common feature in III-V and II-VI semiconductor compounds. For such defects, the annealing rate induced by injection is proportional to the rate of minority carrier trapping. As a result, the study of the annealing rate versus the density of injection and versus the temperature allows us to obtain the minority-carrier trapping cross section and its variation with temperature. The method is illustrated by a study of the so-called E3 defects, created by electron irradiation at room temperature in n-type GaAs. For this defect, we find a minority-carrier cross section which is thermally activated with an activation energy of ∼0.35 eV, implying that the capture of minority carriers, like the capture of majority carriers, occurs through multiphonon emission. A discussion of this result in terms of configuration coordinate diagram shows the limitation of this model.