Novel P-Type Al(In)GaN Superlattice Structures for High-Performance Bipolar Transistors.

For ultra-high power, high temperature electronics, III-N wide-bandgap materials offer substantial advantages over other semiconductor material systems. Remarkable power densities have been achieved in AlGaN-based high electron mobility transistors(HEMTs) for operation at high frequencies. Even higher power densities, with lower noise and better linearity, have been projected for AlGaN/GaN heterojunction bipolar transistors (HBTs). The main issues preventing the realization of suchhigh-performance HBTs are 1) the problem with the p-type doing of the base region and 2) the emitter to collector current leakage. We are proposing a new HBT design with a novel structure in the base layer, to solve the first problem, in conjunction withgrowth on substrates with low density of treading dislocations to address the second issue. We will design and fabricate these HBTs by molecular beam epitaxy (MBE) for high-frequency operation at high temperatures and very high power densities (>10 W/mm). SVT Associates has already demonstrated high temperature (425 oC) operation of nitride---based heterojunction bipolar transistors (HBTs). The proposed new HBT design would eliminate some of the main problems in the high-power and high-frequency operationof these devices. These HBTs will offer high transistor linearity and low phase noise, inherent in bipolar designs, that are required for economically significant digital transmission applications. The chemically and thermally stable, high-powertransistors would have numerous commercial applications in aerospace, automotive, geothermal/oil drilling, portable computation and digital communications industries.