Zinc diffusion in GaAs and zinc-induced disordering of GaAs/AlGaAs multiple quantum wells: a multitechnique study

Abstract

A review of experimental results obtained by different techniques is presented on the problem of zinc diffusion. Zinc diffusion was carried out on Si-doped GaAs (n almost-equal-to 10(18) cm-3) and on multiple quantum well (MQW) structures. The samples were investigated by secondary-ion mass spectroscopy (SIMS), different imaging modes of scanning electron microscopy such as secondary electrons, cathodoluminescence (CL) and electron beam-induced current (EBIC), transmission electron microscopy on a wedge-shaped specimen (WTEM) and by photoluminescence (PL). A nonexponential decay of the low-temperature EBIC signal accompanied by a very low CL signal due to the high density of nonradiative recombination centres were observed in the diffused region of the n-doped GaAs. Indeed, PL measurements demonstrate that Ga vacancies play a key role on the mechanism of the Zn diffusion. On the impurity-induced disordered (IID) MQW samples, an enrichment of Al at the surface was observed by SIMS and confirmed by WTEM and PL. Low-temperature PL spectra show the gradual disappearance of the MQW excitonic transitions as the number of disordered layers increases. When all of the MQW structure is destroyed, the band-to-band recombinations in the IID produced alloy dominate the PL spectrum.