Modeling of InP DHBTs in a Transferred-Substrate Technology with Diamond Heat Spreader

This paper presents a compact model for InP DHBTs in a transferred-substrate technology with a diamond heat spreader. The heat spreading layer is introduced to effectively remove the generated heat from the InP DHBTs but will also have a non-negligible influence on the device characteristics. Thermal vias connecting individual collectors of the InP DHBTs to the heat spreading layer act like open-circuited stubs and the electromagnetic environment of the device access structure is modified by the promixity of the diamond layer. The proposed compact modeling approach includes a multiline TRL calibration procedure using on-wafer structures for a definition of reference planes for model extraction, 3D electromagnetic simulation based extraction of the extrinsic parasitic network associated with via transitions and device electrodes in the presence of the diamond heat-spreading layer and the extraction of the remaining parameters of a large-signal HBT model from multi-bias S-parameters and static characteristics. The compact model is verified using a 500 nm InP DHBT by comparison against measured S-parameters and associated transistor gains in the frequency range up to 220 GHz and large-signal measurements at 94 GHz under class-A operation.