Improved thermal management of InP transistors in transferred-substrate technology with diamond heat-spreading layer

A method to improve the thermal management of indium phosphide (InP) double-hetero bipolar transistors (DHBTs) fabricated in a transferred-substrate technology is presented. A vapour-phase deposited diamond layer acting as a heat spreader is heterogeneously integrated into the vertical layer stack. It is observed that the diamond layer reduces the thermal resistance of a 0.8 × 5 μm² single emitter-finger HBT by roughly 75% down to 1.1 K/mW which is, to the authors´ knowledge, the best value reported thus far for InP HBTs of comparable size. It is also the first demonstration of heterogeneous integration of diamond into an InP HBT monolithic microwave integrated circuit.