Effect of nonuniform doping profile on thermometric performance of diode temperature sensors

Abstract

A theoretical investigation of the influence of a nonuniform doping concentration to the temperature response curve of diode temperature sensors is presented, which is the first effort in this field important for diffused diodes used as the temperature sensors. The current-voltage characteristic, from which the temperature response curve can be obtained, has been calculated using the model of a one-dimensional exponentially graded p-n junction with uniformly doped base region and the diffusion current of the minority carriers through the p-n junction. We show that depending on the doping gradient both contributions to the current coming from the electron and hole current components appear to be of the same order of magnitude. That is in contrast to the prediction of the widely used asymmetrical step junction model. It follows from numerical calculations that an effective shift of the temperature response curve due to nonuniformly doped emitter region in the temperature equivalent can reach the value of about 20 K. The limiting temperature Tm in the temperature response curve that restricts its extent into the high temperature range has been analyzed depending on the excitation current, the doping concentration of the base, and the p-n junction depth.