Low threshold photopumped AlxGa1−xAs quantum-well heterostructure lasers

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Abstract
Data are presented on very low threshold photopumped separate‐confinement quantum‐well heterostructure (SC QWH) lasers grown by metalorganic chemical vapor deposition (MOCVD). An unusually thin single quantum well (size Lz≲ 60 Å) is employed in the QWH with the carriers confined (‘‘trapped’’) in the interior ‘‘cladding’’ region, which serves also as the optical waveguide. Excess carriers, which are photogenerated (or injected), are confined in the thin interior cladding region (size Lz′ ∼1000 Å) and, in this charge reservoir and waveguide region, are thermionically ‘‘emitted’’ back and forth across the well until scattered to lower energy in the well (ΔE∼ℏωLO) and collected. Continuous (cw) 300 K photopumed laser operation of these QWH’s is demonstrated for very short cavities. For one QWH wafer laser operation occurs at λ∼7730 Å with a photopumping threshold of 380 W/cm2 (Jeq ∼160 A/cm2) and for another wafer at λ∼7000 Å with threshold 103 W/cm2(Jeq∼ 410 A/cm2). The photopumped samples are as small as 20×40 μm, thus making these laser thresholds (for such short cavity lengths) a factor of 3–10 better than the lowest previously reported.