Characterization of ion-implantation doping of strained-layer superlattices. I. Structural properties

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Abstract
We have characterized the effects of Be+ implantation and controlled-atmosphere annealing on the structure of Ga(AsP)/GaP strained-layer superlattices (SLSs). Damage and strain distributions within the implanted layers were examined by cantilever-beam bending measurements, double-crystal x-ray rocking curves, and a variety of ion-channeling techniques. Implantation-induced displacement damage produces additional stress in the SLS, in this case reaching 4.5×109 dyn/cm2, a value comparable to that of the built-in stresses in these SLSs. The depth distribution of ion damage as measured by ion channeling agrees well with the predictions of the trim code, although substantial recovery occurs during the room-temperature implant. Rocking curve analysis indicates that the interlayer strain in the SLS is retained despite the ion damage, and that the ion damage can be modelled as an independent additional source of strain in the as-implanted structure. The linear expansion of the layers due to point defect generation for the 1×1015 Be/cm2 implant is determined to be approximately 0.3% by all three techniques. After controlled-atmosphere annealing at the nominal SLS growth temperature, both the x-ray and ion-channeling measurements indicate removal of the implant damage with the as-grown strain retained and no resolvable intermixing of the layers in the SLS. These results demonstrate that ion-implantation technologies developed for bulk semiconductors can successfully be applied to strained-layer superlattice systems.

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