PERFORMANCE OF DOUBLE-HETEROSTRUCTURE UNIPOLAR TRANSISTORS IN HIGH-FREQUENCY POWER APPLICATIONS

The fabrication of a vertical hot electron transistor incorporating a two-dimensional electron gas (2DEG) is demonstrated in the GaAs/AlGaAs materials system. The difficulties caused by the need to form selecti ve ohmic contacts to the different conducting layers have been overcom e using a combination of in situ focussed ion beam (FIB) isolation and molecular beam epitaxial (MBE) regrowth. This has allowed a high yiel d of working devices to be achieved with h(fe) = 4 at 77 K. The high f requency (f(max) approximate to 100 GHz) current drive capability of t his device will be discussed.