InGaAs/AlGaAs intersubband transition structures grown on InAlAs buffer layers on GaAs substrates by molecular beam epitaxy

We report on the use of InAlAs linearly graded buffer layers for improving the performance of InyGa1-yAs (y>0.42)/AlGaAs intersubband transition (ISBT ) superlattice structures grown on GaAs substrates by molecular beam epitax y. Linearly graded InAlAs buffer layers give better optical confinement in the active superlattice region, similar intersubband transition linewidths, and comparable surface morphology compared to linearly graded InGaAs buffe r layers. The best surface morphology for our ISBT superlattices was obtain ed by growing the linearly graded InAlAs buffer layer at 360 degrees C.