Infrared photodetectors fabricated from self-organized quantum dot nanostructures

Abstract

Intersubband carrier transitions in either the conduction or valence bands of III-V semiconductors are important for the design of a new generation of optoelectronic devices. These transitions have been successfully used to demonstrate the operation of a new class of infrared lasers and detectors. In this paper, we discuss the use of intersubband transitions in quantum dot nanostructures for infrared sensing. The quantum dot structures in our work allow the detection of normal-incidence light. This is promising for the design of future focal plane arrays that do not require a grating structure to scatter incident light into the correct polarization for detection via intersubband transitions. The quantum dot infrared photodetectors in this work also exhibit an intrinsic photovoltaic effect. Both photoconductive and photovoltaic operation has been demonstrated at low temperatures (40 K) with responsivities on the order of tens of mA/W for bias voltages less than 0.5 V. Detectivities ranging from 2 X 108 cmHz1/2/W to 7 X 109 cmHz1/2/W have been measured in devices operating in either the photovoltaic or photoconductive mode. We have demonstrated that the quantum dot structures have the capability to detect infrared light in the 9 to 13 micrometers spectral band.