Scientists at the University of Tokyo have reported a new method for electrical cooling that can be executed even in the absence of moving parts. When a bias voltage is applied to quantum wells made of aluminum gallium arsenide, a semiconductor, electrons release some of their heat by a process known as “evaporative cooling.”
Devices based on such a principle could be introduced into electronic circuit boards through conventional semiconductor fabrication techniques to help laptops and smartphones prevent performance issues due to high temperatures.
Buyers have a liking for portable electronics. However as tablets, smartphones, and laptops become smaller and more robust, the chance of getting overheated becomes an ever more serious concern. Existing fans are bulky and noisy, and include moving parts that can fail.
Currently, researchers at the Institute of Industrial Science, the University of Tokyo, have come up with a new, solid-state solution produced from semiconductors that can be easily made directly into laptops or smartphones.
Modern portable devices have enabled the current information revolution. However, this miniaturization comes with inherent challenges from the waste heat produced. Our new system allows for on-chip cooling using standard semiconductor fabrication processes.
Marc Bescond, Study First Co-Author, Institute of Industrial Science, The University of Tokyo
Quantum wells are nanostructures adequately small to trap electrons. The kind of quantum well used in this study is known as an asymmetric double-barrier heterostructure. In such devices, gallium arsenide wells, which are extremely narrow, are isolated by aluminum gallium arsenide layers.
When the applied bias voltage equals the quantum level energy within the well, electrons can pass through a barrier by using resonant tunneling, without any difficulty. But only the electrons with high kinetic energies can continue to pass the second barrier. The device becomes cooler because the “hotter” fast-moving electrons escape, whereas the “cooler” slow electrons become trapped.
Such “evaporative cooling” is similar to the process that makes one feel cold while stepping out of a swimming pool. The water molecules with high thermal energy are the first to evaporate from the skin, taking the heat along with them.
We have achieved electron cooling of up to 50 degrees centigrade under ambient conditions. These results make our quantum well devices promising for comprehensive heat management in smart devices. Future smartphones may come with internal circuit boards packed with even more components, as long as they also have some of these cooling quantum wells.
Kazuhiko Hirakawa, Study Senior Author, Institute of Industrial Science, University of Tokyo