THERMAL MANAGEMENT OF MICROWAVE-POWER HETEROJUNCTION BIPOLAR-TRANSISTORS

A comprehensive study of the device layout effects on thermal resistan ce in thermally-shunted heterojunction bipolar transistors (HBTs) was completed. The thermal resistance scales linearly with emitter dot dia meter for single element HBTs. For multiple emitter element devices, t he thermal resistance scales with area. HBTs with dot geometrics have lower thermal impedance than bar HBTs with equivalent emitter area. Th e thermal resistance of a 200 mu m(2) emitter area device was reduced from 266 degrees C/W to 146 degrees C/W by increasing the shunt thickn ess from 3 mu m to 20 mu m and placing a thermal shunt landing between the fingers. Also, power-added efficiencies at 10 GHz were improved f rom 30% to 68% by this thermal resistance reduction. Published by Else vier Science Ltd.