Techniques and applications of graded‐composition InGaAlAs alloys

As molecular‐beam epitaxy crystal growth techniques steadily progress from the research stage into full‐scale production, the need for precise control of the crystal growth process becomes increasingly important. This is particularly true for epitaxial layer structures requiring precisely controlled compositional gradients. We have developed techiques for the growth of linearly graded InGaAlAs, while precisely maintaining lattice matching to the InP substrate, such that x‐ray full widths at half‐maximum close to the theoretical limit have been achieved. Through the use of these techniques, heterojunction bipolar transistors and graded‐index separate confinement heterostructure laser diodes have been grown, fabricated, and tested.