Hot-electron photodetectors show poor photoelectric performance due to the limitation of the small number and low energy of hot electrons. Traditional phototransistors use electricity to drive the transport of hot electrons and control photocurrent. However, the existence of defects leads to a slow response rate, voltage drive leads to a significant increase in dark current, and an electrical drive system is required.

In a new research, a team led by Prof. FEI Guangtao and Prof. XU Shaohui from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences realized enhancement and fast stabilization of hot-electron photocurrent of all-optical-input transistors with the regulation of ultraviolet light. The result was published on the journal of physical chemistry C.

"We introduced an ultraviolet light (gate light) to regulate the hot-electron photocurrent, which was excited by infrared light (source light)," said LIU Shuli, first author of the paper, "due to Schottky barrier-tuning effect and trap-filling effect, hot-electron photocurrent in the Au electrode could be amplified tens of times, and response rate could also be improved."

As the power of the gate light increases, the enhanced photocurrent reaches a stable state quickly. It is beneficial to understand and regulate the surface state of semiconductors in optoelectronic fields.

Considering that this type of transistor can work without electric support, it can be used in special environments that prohibit the use of electricity. Moreover, this interesting feature will make devices more reliable and will meet the demands of energy-saving and low-carbon age.

This work was supported by the National Natural Science Foundation of China.

Fig.1 (a) The I-t curve of hot-electron photocurrent generated by infrared light (Source light, PS) output by the transistor under ultraviolet light (Gate light, PG) modulation (illustration is the schematic diagram of the transistor), (b) the current output when PG and infrared PS light with different power intensity are illuminated on the transistor, (c) I-t response curves under PS with and without PG. (Image by XIA Kai)