ION DAMAGE BUILDUP AND AMORPHIZATION PROCESSES IN GAAS-ALXGA1-XAS MULTILAYERS

The nature of ion damage buildup and amorphization in GaAs-AlxGa1-xAs multilayers at liquid-nitrogen temperature is investigated for a varie ty of compositions and structures using Rutherford backscattering-chan neling and cross-sectional transmission electron microscopy techniques . In this multilayer system, damage accumulates preferentially in the GaAs layers; however, the presence of AlGaAs enhances the dynamic anne aling process in adjacent GaAs regions and thus amorphization is retar ded close to the GaAs-AlGaAs interfaces even when such regions suffer maximum collisional displacements. This dynamic annealing in AlGaAs an d at GaAs-AlGaAs interfaces is more efficient with increasing Al conte nt; however, the dynamic annealing process is not perfect and an amorp hous phase may be formed at the interface above a critical defect leve l or ion dose. Once an amorphous phase is nucleated, amorphization pro ceeds rapidly into the adjacent AlGaAs. This is explained in terms of the interplay between defect migration and defect trapping at an amorp hous-crystalline or GaAs-AlGaAs interface. In addition, enhanced recry stallization of the amorphous GaAs at the interface may occur during h eating if an amorphous phase is not formed in the adjacent AlGaAs laye r. This is most likely the result of mobile defects injected from the AlGaAs layer during heating. (C) 1996 American Institute of Physics.