Type-II GaAsSb/InGaAs/GaAsP Strain-Compensated ‘W’ Multi-Quantum Wells for GaAs-Based VCSELs

‘W’ type-II GaAs<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.88</inf>Sb<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.12</inf>/In<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</inf>Ga<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.7</inf>As multi-quantum well (MQW) structures with GaAs<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.6</inf>P<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.4</inf> strain compensating layers are grown on GaAs (001) substrates by molecular beam epitaxy (MBE). The effect of QW thicknesses on the structural and optical properties of these ‘W’-MQWs is studied. At room temperature (RT), photoluminescence (PL) emission at around 1010 nm, observed in a 14 nm-GaAsSb/2.5 nm-InGaAs 'W'-MQW, extends to around 1120 nm with a thinner 8.5 nm-GaAsSb/1.7 nm-InGaAs ‘W’-MQW configuration. Cross-sectional transmission electron microscopy (TEM) and x-ray rocking curve (XRC) analysis validate the experimental QW thicknesses and material compositions. The simulations of this ‘W’-MQW system with different QW thicknesses indicate that the thinner QW effectively increases wavefunction overlap. However, thinner than the optimum QW thickness, especially for InGaAs, interface roughness and compositional fluctuation in the QW become more important and can reduce the structural and optical properties of the MQW.