Band-gap engineering for new photonic and electronic devices.

Band-gap engineering is a powerful technique for the design of new semiconductor materials and devices. Heterojunctions and modern growth techniques, such as molecular beam epitaxy, allow band diagrams with nearly arbitrary and continuous band- gap variations to be made. A new generation of devices with unique capabilities, ranging from solid-state photomultipliers to resonant tunneling transistors and spin polarized electron sources is emerging from this approach.