Article comprising a strained layer quantum well laser

An article comprising a GaAs-based self-aligned semiconductor laser adapted for emission of electromagnetic radiation of wavelength .lambda., said laser comprising a semiconductor substrate, a multiplicity of epitaxial semiconductor layers on said substrate, and first and second contact means for flowing a current between said contact means, said multiplicity of semiconductor layers comprising, in sequence, a first semiconductor layer (to be referred-to as the "first cladding layer") doped to exhibit a first conductivity type, a second semiconductor layer (to be referred-to as the "active layer") that is substantially undoped, a third semiconductor layer (to be referred-to as the "second cladding layer") doped to exhibit a second conductivity type, and a patterned fourth semiconductor layer (to be referred-to as the "blocking layer"), at least a part of said blocking layer material being doped to exhibit conductivity of said first conductivity type, said blocking layer being patterned to define a window adapted to facilitate, under forward bias laser operating conditions, flow of charge carriers from a contact region through said second cladding layer into said active layer, said blocking layer adapted to substantially prevent, under said forward bias laser operating conditions, flow of charge carriers through said blocking layer material into said second cladding;

• characterized in that
• a) 0.87 .mu.m <.lambda..ltorsim.1.1 .mu.m;
• and
• b) said active layer comprises at least one quantum well, of thickness t less than a critical thickness t.sub.c associated with dislocation formation, sandwiched between two barrier layers, associated with the material of each of said quantum well and barrier layers being an equilibrium lattice constant, with said quantum well material selected such that said equilibrium lattice constant associated with said quantum well material differs from said equilibrium lattice constant associated with said barrier layer material.