Electron Beam Source Molecular Beam Epitaxy of AlxGa1-x as Graded Band Gap Device Structures

A new method has been developed for the growth of graded band-gap AlxGa1-x As 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 AJ evaporation rates. The large dynamic response of the metal sources enables for the first time the synthesis of variable band-gap AlxGa1-xAs with arbitrary composition profiles. This new technique has been demonstrated in the growth of unipolar hot electron transistors, graded base bipolar transistors, and M-shaped barrier superlattices.