Microwave heterojunction bipolar transistors with emitters designed for high power applications and method for fabricating same

Generally, and in one form of the invention, an emitter structure for a bipolar transistor is disclosed. The structure comprises an emitter layer 14 of AlxGa1-xAs, where x > 0.4, abutting a base layer 16. In another form of the invention a bipolar transistor is disclosed. The transistor comprises a substrate 11, a subcollector layer 20, a collector layer 18, a base layer 16, and an emitter layer 14 of AlxGa1-xAs, where x > 0.4. An advantage of the invention is that the AlGaAs layer acts as both a ballast resistor and as the active emitter for the transistor.