Instability of partially disordered carbon-doped AlGaAs/GaAs superlattices

Superlattices of Al_0.3Ga_0.7As/GaAs grown by metalorganic chemical vapor deposition and heavily doped with carbon using CCl₄ were annealed for 24 h at 825°C under a variety of ambient and surface encapsulation conditions. Pronounced changes in photoluminescence from the annealed superlattices with storage time at room temperature, as opposed to an excellent reproducibility of that from the as-grown, not annealed samples, are reported. These changes may be indicative of degraded thermal stability of the annealed superlattice crystals due to high-temperature-induced lattice defects. The systematic failure to fabricate buried-heterostructure quantum well lasers via impurity-induced layer disordering in similarly doped AlGaAs/GaAs crystals, which may be related to the same effect, is also discussed.