The metal-organic vapour phase epitaxy growth of GaInAsP and GaAlInAs based graded refractive index separate confinement heterostructure multiple quantum well lasers incorporating linearly graded confinement layers

Abstract

The epitaxial growth of long wavelength graded refractive index separate confinement heterostructure multiple quantum well (GRIN-SCH MQW) lasers by low pressure metal-organic vapour phase epitaxy is described. By varying the group III and group V gas flows simultaneously it was possible to produce GaInAsP material that was linearly graded between the solid phase compositions of InP and Ga0.18In0.82As0.40P0.60 (λ = 1.15 μm). This was achieved using experimental data for the growth of InP and GaInAsP at λ = 1.07 and 1.15 μm, together with a knowledge of the alloy composition vs. band gap relationship. The laser material was characterized by double-crystal X-ray diffraction using the (004) reflection (Δa/a = 580 ppm), photoluminescence spectroscopy (39 and 11 meV full width at half-maximum line-widths at 300 and 10 K respectively) and cross-section transmission electron microscopy (well and barrier thicknesses of 70 and 65 A respectively), which showed that the material was of high quality with compositionally abrupt heterointerfaces and precisely defined quantum wells. Auger electron and secondary ion mass spectrometry were used to confirm the grade linearity. High quality, linearly graded GaAlInA structures were also produced. Device results on GRIN-SCH MQW lasers are reported for which continuous wave threshold currents of 13.3 mA were obtained.