Laterally-biased quantum dot infrared photodetector

At the Air Force Research Laboratory, Space Vehicles Directorate, we are interested in improving the performance of or modifying the capabilities of infrared detectors in order to locate and identify dim and/or distant objects in space. One characteristic we are very interested in is multicolor detection. To this end, we have turned to a novel detector design that we have come to call a Lateral Quantum Dot Infrared Photodetector (LQDIP). In this design, InAs quantum dots are buried in a GaAs quantum well, which in turn is tunnel-coupled to another GaAs quantum well. Photoexcited electrons from the quantum dots tunnel over to the second well and are then swept out via a lateral (perpendicular to the growth direction) bias voltage. This architecture should exhibit the ability to tune to select infrared frequencies with reduced dark current and unity gain. The lateral photocurrent is directed by a vertical (parallel to the growth direction) gate voltage. We will discuss this detector architecture and the LQDIP operating principles and conditions, and we will present some preliminary results of current–voltage, photocurrent, differential conductance, and spectral measurements.

► Describe Lateral QDIP concept, growth structure, and device layout.
► Show dark I-V results and operation of pinch-off gate.
► Differential conductance shows a single step and multiple quantum dot oscillations.
► Preliminary optical I-V shows possible SNR increase with increasing gate bias.
► Spectral response increases then decreases as tune through resonant tunneling level.