Quantum-Dot Infrared Photodetectors

Abstract

Mid- and far-infrared detectors operating at elevated temperatures (T > 150 K) are critical for imaging applications. In(Ga)As/GaAs quantum dots, grown by self-organized epitaxy, are an important material for the design and fabrication of high-temperature infrared photodetectors. Quantum dot infrared photodetectors (QDIPs) allow normal-incidence operation, in addition to low dark currents and multispectral response. The long intersubband relaxation time of electrons in quantum dots improves the responsivity of the detectors, contributing to better high-temperature performance. These devices also exhibit photoconductive gain. The characteristics of state-of-the-art lateral and vertical QDIPs will be described. We have achieved peak responsivity for wavelengths ranging from 3.7-18 μm. We have also obtained extremely low dark currents (I dark = 27 pA, T = 100 K, V bias = 0.5 V), high detectivities (D* = 2.9x10 8 cmHz 1/2 /W, T = 100 K, V bias = 0.2 V), and high operating temperatures (T = 150 K) for these quantum-dot detectors. The excellent performance of these devices at low bias voltages indicates the compatibility of high-temperature QDIPs with commercially available silicon read-out circuits for imaging focal plane arrays. These results, as well as infrared imaging with QDIP arrays, will be described and discussed.