Carrier lifetimes in low-resistivity GaAs upon electron bombardment and annealing

Single crystals of GaAs, n- and p-type, were bombarded with 1 MeV electrons at 78 °K. By photoconductivity and photomagnetoelectric measurements, a decrease of majority and minority carrier lifetime was detected in all cases. The bombardment dose was small and hence the changes of carrier concentration and mobility were insignificant. The decrease of lifetimes is hence due solely to the increase of the number of recombination and trapping centres. Isochronal annealing experiments showed a complete, more or less, recovery for n-type specimens at about 300 °K, while the revocery of p-type specimens is expected to occur at higher temperatures. The recovery takes place through three normal annealing stages for both types of specimens, in accordance with the Fletcher and Brown theory. We found also discrete reverse annealing stages at temperatures usually below each normal annealing stage. This is attributed to the increase of the activity of the recombination and trapping centres due to a rearrangement of the associated defects to more stable states.