Integrated Hot-Phonon Harvesting Barriers in High-Power Circuit Devices

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CBET 1332807PI: Massoud Kaviany (U. Michigan)The proposed research aims to use (integrate) a novel hot phonon absorption barrier structure converting phonon energy to harvestable electric potential, in high-power electric circuits and devices. This electric potential barrier (barrier is formed by heterostructures, e.g., Al alloying, and its height matches optical phonon energy) allows only those electrons with high momentum/energy to pass through it, while the remaining electrons with lower energy will have a favorable phonon absorption condition. For the proposed example of GaN high electron mobility transistor, the expected reduction in the maximum operating temperature is as much as 40 degC at 5 W/mm Joule heating rate, and up to 20% of the phonons will be recycled corresponding to the same saving in power consumption (i.e., in-situ direct conversion of emitted phonons back to electric potential energy). The results are expected to also apply to light emitting diodes and other high-power electronics, and contribute to thermal management at atomic scale.The use of a heterobarrier, or abrupt change in material composition, in a circuit allows electricity-generated heat to boost electric potential instead of draining efficiency. Using this architecture in high-power circuits lowers the device temperature and improves the device efficiency. Electrons in a circuit gain energy by absorbing phonons, the interatomic vibrations associated with heat. In a circuit, a ?heterobarrier? may be inserted to take advantage of these excited electrons, boosting them up in electrical potential. The heterobarrier is engineered such that the increase in the band gap energy of the new material is equal to the energy given the electron by the phonons. Monte Carlo simulations based on interaction kinetics between electron and phonon show up to 19% of phonon energy converts to electric potential. This heterobarrier reverses the role of phonon from causing electric potential drop to causing potential gain.