Optimization of buffer layers for InGaAs/AlGaAs PIN optical modulators grown on GaAs substrates by molecular beam epitaxy

In this work we compare the effect of the buffer layer on the device qualit y and surface morphology of strained InGaAs/AlGaAs PIN multiple quantum wel l (WQW) modulators, We examine GaAs buffer layers and linearly graded InGaA s buffer layers. Our results indicate that for lower indium concentrations in the quantum wells (less than about 23%) better device performance and su rface morphology are obtained by growing directly on GaAs. PIN MQWs with in dium mole fractions higher than about 24% have better. properties when a li neal-ly graded buffer layer is used.