The Effect of Barrier Composition on the Vertical Carrier Transport and Lasing Properties of 1.55-<tex>$mu hbox m$</tex>Multiple Quantum-Well Structures

Abstract

In this paper, the effect of barrier bandgap and composition on the optical performance of 1.55-mum InGaAsP/InGaAsP and InGaAsP/InGaAlAs multiple quantum-well structures and Fabry-Perot lasers is evaluated experimentally. Direct vertical carrier transport measurements were performed through strain-compensated multiple quantum-well (MQW) test structures using femto-second laser pulse excitation and time-resolved photoluminescence up-conversion method. MQW test structures were grown with different barrier composition (InGaAsP and InGaAlAs) and barrier bandgap (varied from lambda <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> = 1440 to 1260 nm) having different conduction band DeltaE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> and valence band discontinuity DeltaE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</sub> , while keeping the same InGaAsP well composition for all the structures. The ambipolar carrier transport was found to be faster in the structures with lower valence band discontinuity DeltaE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</sub> . Regrown semi-insulating buried heterostructure Fabry-Perot (SIBH-FP) lasers were fabricated from similar QWs and their static light-current-voltage characteristics (including optical gain and chirp spectra below threshold) and thermal characteristics were measured. Lasers with InGaAlAs barrier showed improved high-temperature operation, higher optical gain, higher differential gain, and lower chirp, making them suitable candidates for high-bandwidth directly modulated uncooled laser applications