GaAs Quantum-Wire Laser Using Fractional Layer Superlattice

In (AlAs) k/n (GaAs) l/n (k+l=n) fractional layer superlattice (FLS) growth on the (001) GaAs vicinal surface 2° off toward [1̄10] by metal-organic chemical vapor deposition, using a (AlAs) m (GaAs) n (m, n>3) short period superlattice as the buffer layer very much improve the uniformity of lateral periodicity in the FLS near the FLS/buffer interface compared with using binary (GaAs and AlAs) and ternary AlGaAs as the buffer layers. This is due to the improvement in the uniformity of the terrace width on the surface of a short period superlattice by step-ordering. As a result, a large polarization anisotropy of about 50% is observed in the photoluminescence spectrum for the quantum-wire array structure oriented toward [110] in which a 4-nm-thick (AlAs)1/4(GaAs)3/4 FLS layer is sandwiched by (AlAs)3(GaAs)3 short period superlattice layers. Separated confinement heterostructures consisting of a 12-nm-thick undoped (AlAs)1/4(GaAs)3/4 FLS quantum-wire active layer, doped (AlAs)1(GaAs)2 carrier confinement layers, and doped Al0.6Ga0.4As optical confinement layers are grown. To prevent the disordering of the FLS layer induced by the diffusion of intentionally doped impurity atoms during the growth and the processing, low-diffusive Si and C atoms are used for n- and p-type doping into carrier and optical confinement layers. Lasing operation is obtained by current injection below 195 K for the electrode with simple stripe geometry. The lasing wavelength depends on the orientation of the stripe electrode. The electrode with [110] orientation which is parallel to the quantum wire array has a lasing wavelength of 662 nm, and the [1̄10] orientation which is perpendicular to the array has a lasing wavelength of 667 nm at 10 K.