Direct observation of the principal deep level (EL2) in undoped semi-insulating GaAs

Abstract

A high spatial resolution, near infrared absorption method has been used to determine [EL2] concentrations in semi-insulating undoped Czochralski liquid encapsulated (LEC) GaAs. Fine structure superimposed on the well-known ‘‘W’’ distribution across 〈110〉 diameters of {001} wafers has been detected. Fine structure has also been directly observed in {110} sections of ingots grown along 〈001〉 using a CCTV vidicon system to observe transmitted infrared radiation. The structure consists of narrow bands of increased absorption which correspond with high densities of dislocations in the same specimens.