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 epitaxy. 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 buffer layers. The best surface morphology for our ISBT superlattices was obtained by growing the linearly graded InAlAs buffer layer at 360 degrees C.