TRANSMISSION ELECTRON-MICROSCOPY STUDY OF MICRODEFECTS IN DISLOCATION-FREE GAAS AND INP CRYSTALS

The transmission electron microscopy study has been carried out to characterize the structural defects in heavily impurity-doped LEC-grown GaAs and InP crystals which are free from native dislocations. The microdefects in S- and Te-doped GaAs crystals were found to be mainly Frank-type stacking faults and prismatic dislocation loops. Diffraction contrast analysis revealed that all the microdefects were of interstitial type. However, in Zn-doped GaAs and Zn-, S-, and Te-doped InP crystals, the microdefects were hardly observed, which suggests that those crystals could be useful substrates for electronic devices. The appearance, especially in GaAs : S, of microdefects and also of helical dislocations associated with the effects of impurities on reducing dislocations are discussed.