Thin upper-confining layer AlxGa1−xAs-GaAs quantum well heterostructure laser diodes

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Abstract
AlxGa1−xAs‐GaAs quantum well heterostructure (QWH) laser diodes with much thinner upper confining layers (0.6, 0.45, 0.3, and 0.2 μm) than usual (1–2 μm) are demonstrated. The diodes exhibit well behaved transverse far‐field patterns, low broad‐area pulsed threshold current densities, and high differential quantum efficiencies. The diodes with thinnest upper confining layers, ∼0.2 μm, have broad‐area pulsed threshold current densities as low as Jth∼169 A/cm2 and a total external differential quantum efficiency ηT∼53% (∼500 μm long cavities). Stripe‐geometry (40 μm wide) laser diodes made from the crystals with 0.2 μm upper confining layers exhibit room‐temperature continuous (cw) threshold currents of 60 mA, output powers of ∼200 mW/facet (uncoated), and transverse far‐field patterns with a full angle half power (FAHP) of 48°. Nonoptimized narrow‐stripe (∼4 μm) native‐oxide index‐guided laser diodes fabricated on the same 0.2 μm confining layer QWH crystal operate at pulsed thresholds as low as 9 mA and continuous thresholds of 16 mA, with total external differential quantum efficiencies of 39% pulsed and 30% cw.