ABSTRACTA new method has been developed for the growth of graded band-gap AlxGal-xAs alloys by molecular beam epitaxy which is based upon electron beam evaporation of the Group III elements. The metal evaporation rates are measured real-time and feedback controlled using beam flux sensors. The system is computer controlled which allows precise programming of the Ga and Al evaporation rates. The large dynamic response of the metal sources enables for the first time the synthesis of variable band-gap AlxGal-.xAs with arbitrary composition profiles. This new technique has been demonstrated in the growth of unipolar hot electron transistors, graded base bipolar transistors, and Mshaped barrier superlattices.
