To Catch One Photon

Abstract

APPLIED PHYSICS Research fields as diverse as spectroscopy, materials characterization, and quantum optics are increasingly dependent on the capability of detecting single photons. These photons usually are detected by photomultiplier tubes or avalanche processes. A single absorbed photon creates an electron-hole pair, which is then separated and accelerated in an electric field to create a cascade of free charges as they collide with other atoms in the material. Shields et al. introduce a solid-state, single-photon detector that combines the charge storage effects of quantum dots with the gate-controlled conductivity of thin film transistors. A layer of quantum dots placed near the electron conduction channel of a field effect transistor is loaded with electrons, the induced electric field of which depletes the underlying conduction channel of electrons. The hole of the electron-hole pair created by the incoming photon recombines with an electron trapped in the quantum dot, which adds an extra electron to the conduction channel. The conductivity of the channel increases in steps as single photons are detected. — ISO Appl. Phys. Lett . 76 , 3673 (2000).