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CRIEPI proposes next-generation high-performance optical sensor new principles for field effect transistors

On February 6, the Central Research Institute of Electric Power Industry (CRIEPI) announced that a field effect transistor manufactured using semiconductor nano crystals with a dual structure has a large photocurrent amplification effect the exceeds that of conventional devices.

Core shell type nano crystal and thin film transistor construction schematic diagram

Joint research was conducted with Waseda University and the Swiss Fluxim AG Group. A field effect transistor is a basic element used in a variety of electronic circuits and devices and they are also used as sensors since the current flowing through them changes in response to external stimuli, such as environmental changes and light irradiation.

The research group aimed to increase the photoresponsivity of field effect transistors by fabricating nano crystals on the 10nm diameter level with a dual structure consisting of a core of cadmium and selenium and a shell of cadmium and sulfur. Test were conducted to vary the core diameter and shell thickness to change the physical and chemical properties. Measurements of the change in current when the fabricated transistors are illuminated with ultraviolet light showed that the current in thin film of several levels increased by 10,000 times. The current amplitude was larger than that of any field effect transistor using materials known to date showing they have a high potential as optical sensors.

Although these research results will not immediately lead to actual devices, they propose new principles for high-performance optical sensors and is research that will lead to developing optical sensors with high photoresponsivity in the future. The research results will be published on January 29 in Advanced Electronic Materials, a journal for German electronic materials research.

Current increasing due to light irradiation (left), current changing in response to film thickness and gate voltage (right)

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