A NEW SELF-ALIGNMENT TECHNOLOGY USING BRIDGED BASE ELECTRODE FOR SMALL-SCALED ALGAAS/GAAS HBTS

The fabrication and characterization of a new self-aligned HBT utilizing Bridged Base-electrode Technology (BBT) are presented. This new technology simplifies the fabrication process and relaxes the limitations in device size scaling, thus decreasing the emitter size to 1-mu-m x 1-mu-m. In spite of a large junction periphery/area ratio, a good current gain of more than 10 is obtained in an HBT with an emitter size of 1-mu-m x 1-mu-m. A series of fabricated HBT's shows excellent high-speed performance. The highest values of f(T) = 90 GHz and f(max) = 63 GHz are obtained in an HBT with an emitter size of 1-mu-m x 5-mu-m. The realization of HBT's with small emitters and excellent high-frequency characteristics demonstrates the effectiveness of this new technology.