A Simple Extraction Method of Thermal Resistance in Multifinger GaAs HBT

A novel extraction method to estimate the thermal resistance (R
_th
) of a multifinger GaAs heterojunction bipolar transistor (HBT) device is presented based on the simplified Fourier's law. By calculating the thermal coupling resistance between the fingers on top of the self-heating thermal resistance, the values of R
_th
of multifinger devices for various dimensions are accurately calculated while maintaining the simplicity of calculation. To verify the idea, the proposed method is compared with the measurement-based method as well as the analytic methods, such as the finite-element method and the solution of 3-D Laplace's equation. For four-finger HBT devices, the extracted R
_th
results showed good agreements with the analytic methods within an error of 9% and the measurement-based results with a deviation of 7.4%, thus convincing the usefulness of the proposed method.