NUMERICAL SIMULATION OF HIGH SPEED HETEROSTRUCTURE BIPOLAR TRANSISTORS

THIS DOCUMENT DISCUSSES A PROPOSED PROGRAM FOR THE TWO DIMENSIONAL NUMERICAL SIMULATION OF A HETEROJUNCTION ALGAAS/GAAS BIPOLAR TRANSISTOR WITH A WIDE-GAP EMITTER. HBT'S OFFER CONSIDERABLE REDUCTION IN SWITCHING SPEEDS AND IMPROVEMENTS IN CUT-OFF FREQUENCIES OVER THEIR HOMOJUNCTION COUNTERPARTS AND MAY ULTIMATELY PROVIDE SIGNIFICANT COMPETITION TO HIGH ELECTRON MOBILITY TRANSISTOR IN SWITCHING SPEEDS AT ROOM TEMPERATURE. HBT'S FABRICATED USING MBE TECHNOLOGY HAVE BEEN REPORTED TO OPERATE AT CUT-OFF FREQUENCIES ABOVE 10GHZ, AND VALUES AS HIGH AS 100GHZ, ARE EXPECTED FROM OPTIMIZED STRUCTURES. THE KEY TO ACHIEVING THE ANTICIPATED HIGH FREQUENCY PERFORMANCE IS THE ABILITY TO PROVIDE INFORMATION ON DEVICE CHARACTERISTICS AND OPTIMIZATION OF THE CONTROLLING PRIOR TO FABRICATION. THIS PROPOSAL ADDRESSES THE ABOVE NEEDS VIA NUMERICAL SIMULATION. IT IS PROPOSED TO EXAMINE THE ELECTRICAL CHARACTERISTICS OF AN ALGAAS/GAAS HBT VIA THE SOLUTION OF DRIFT AND DIFFUSION EQUATIONS IN TWO DIMENSIONS. ALSO ADDRESSED HERE, IS THE EFFECT OF GRADING THE HETEROSTRUCTURE BIPOLAR DEVICES.