RESIDUAL OXYGEN LEVELS IN ALGAAS/GAAS QUANTUM-WELL LASER STRUCTURES - EFFECTS OF SI AND BE DOPING AND SUBSTRATE MISORIENTATION

Oxygen forms nonradiative recombination centers in GaAs and AlGaAs, and is a common contaminant in AlGaAs, irrespective of the growth technique. We find that O tends to accumulate near the GaAs active region of an AlGaAs/GaAs quantum-well laser prepared by molecular beam epitaxy. Moreover, the Be-doped Al0.6Ga0.4As cladding layer has a higher O content than its Si-doped counterpart. We present evidence that Si-doping suppresses, and Be doping favors incorporation of O in AlGaAs. In undoped and Si-doped AlGaAs, the incorporation of O is further reduced by tilting the (100) GaAs substrates towards <111>A. We propose that Be forms stable Be-O complexes in AlGaAs, and thus, there is virtually no desorption of incorporated O. But in Si-doped AlGaAs, O content is reduced due to reaction between group III suboxides and Si, resulting in the formation and desorption of volatile SiO (g). The study suggests that Be doping should be avoided in the p-side of the GRIN region of a laser structure.