ANGULAR-DEPENDENCE OF DEFECTS INTRODUCED IN GAAS BY ALPHA-PARTICLE BOMBARDMENT

It is commonly assumed that ion beams used for channelling experiments create little damage when moving along a principal axial channel of a crystal. We have employed deep level transient spectroscopy (DLTS) to characterise the defects induced by 300 keV He-ions in 3 GaAs crystal when entering it along the [100] axis (hyperchannelling: alpha(i) = 0 degrees) as well as at small angles with respect to this axis (alpha( i) less than or equal to 1.2 degrees). The results we obtained indicat e that the commonly observed alpha-particle induced defects in Si-dope d GaAs (AsvIAs pairs, isolated As-V and a Si-related metastable defect ) were introduced at all angles of incidence investigated. The concent ration of these defects was a minimum for alpha(i) = 0 and increased w ith increasing angle of incidence. Finally, we observed a difference b etween the relative concentrations of defects introduced during hyperc hannelling and during bombardment off the channel axis.