Low-threshold operation of AlGaAs/GaAs multiple quantum well lasers grown on Si substrates by molecular beam epitaxy

Abstract
We report the first AlGaAs-GaAs multiple quantum well (MQW) lasers fabricated on (001)Si substrates by molecular beam epitaxy (MBE) with relatively thin buffer layers. The lasers have broad-area (170×240 μm) pulsed threshold current density of 3.2 kA/cm2 at room temperature, the lowest ever reported for GaAs lasers grown by MBE on Si. Stripe lasers exhibit external differential quantum efficiencies comparable to those of GaAs lasers grown on GaAs substrates. Clean single longitudinal mode oscillations are observed, with transverse electric field the dominant polarization. The lasers also exhibit well-behaved fast pulse response, with a measured carrier lifetime of ∼2.2 ns in the active region. The improved performance is attributed to the employment of graded-index MQW structures and improved growth techniques.