Transient enhanced intermixing of arsenic-rich nonstoichiometric AlAs/GaAs quantum wells

The superlattice intermixing of arsenic-rich nonstoichiometric AlAs/GaAs quantum wells grown at lowsubstrate temperatures around 300 °C is enhanced by several orders of magnitude relative to diffusion in stoichiometric structures grown at ordinary substrate temperatures. The transient enhanced intermixing is attributed to a supersaturated concentration of group-III vacancies grown into the crystal by low-temperature growth conditions. The enhanced diffusion decays during moderate-temperature annealing between 600 °C and 900 °C for annealing times between 30 and 1000 s. First-order and second-order decay kinetics were both found to agree equally well with diffusion data obtained from isochronal and isothermal annealing. However, both of these kinetics require a thermally activated annihilation enthalpy to explain temperature-insensitive behavior observed in the time-dependent diffusion coefficient. The activation enthalpy Ha for the decay is between 1.4 and 1.6 eV, which is compared with the migration enthalpy Hm51.8 eV of the gallium vacancy in GaAs. For the strongest annealing, the diffusion length approaches the self-diffusion values observed in isotopic superlattices of stoichiometric GaAs. @S0163-1829~99!03439-6#