MBE growth of extremely high-quality GaAs–AlGaAs GRIN-SCH lasers with a superlattice buffer layer

It was found that a thick AlGaAs layer grown on a GaAs–AlGaAs superlattice buffer layer does not affect the optical quality of single quantum well structure successibly grown on the AlGaAs layer; that is, background impurities such as carbon and oxygen, which would come from residual gases, do not accumulate on the AlGaAs surface during molecular beam epitaxy (MBE) growth. Extremely high-quality GaAs–AlGaAs GRIN-SCH lasers were obtained by introducing a superlattice buffer layer. The minimum threshold current density of 175 A/cm2 was achieved for a broad-area Fabry–Perot laser with a cavity length of 450 μm at room temperature. This is the lowest threshold current density of semiconductor lasers with a similar cavity length.