Carrier transport in III–V quantum-dot structures for solar cells or photodetectors**Project supported by the National Natural Science Foundation of China (Grant Nos. 11574362, 61210014, 11374340, and 11474205) and the Innovative Clean-Energy Research and Application Program of Beijing Municipal Science and Technology Commission, China (Grant No. Z151100003515001).

Abstract

According to the well-established light-to-electricity conversion theory, resonant excited carriers in the quantum dots will relax to the ground states and cannot escape from the quantum dots to form photocurrent, which have been observed in quantum dots without a p–n junction at an external bias. Here, we experimentally observed more than 88% of the resonantly excited photo carriers escaping from InAs quantum dots embedded in a short-circuited p–n junction to form photocurrent. The phenomenon cannot be explained by thermionic emission, tunneling process, and intermediate-band theories. A new mechanism is suggested that the photo carriers escape directly from the quantum dots to form photocurrent rather than relax to the ground state of quantum dots induced by a p–n junction. The finding is important for understanding the low-dimensional semiconductor physics and applications in solar cells and photodiode detectors.