DISLOCATION NUCLEATION MECHANISM AND DOPING EFFECT IN P-TYPE ZNSE GAAS/

Nitrogen doped ZnSe/GaAs heterostructures grown at 150 and 250-degrees -C were studied by transmission electron microscopy (TEM). The density of threading dislocations and the interfacial dislocation structure i n ZnSe/GaAs heterostructures are related to the N-doping concentration . In addition, in-situ TEM heating studies show that Frank partial dis locations formed below critical thickness in N-doped ZnSe/GaAs are the sources for nucleation of a regular array of misfit dislocations at t he ZnSe/GaAs interface. By the dissociation of the Frank partial dislo cations and interaction reactions between the dislocations, the 60-deg rees misfit dislocations form. The Frank partial dislocations bound st acking faults which usually form in pairs at the film/substrate interf ace. The density of stacking faults increases with increasing N-doping concentration. Thus, at high N-doping levels, the dislocation nucleat ion sources are close together and not all of the Frank partial disloc ations dissociate, so that a high density of threading dislocations re sults in samples with high N-doping concentrations. The high density o f threading dislocations in the ZnSe film are found to be associated w ith a reduction or saturation of the net carrier density.