Minority Electron Unipolar Photodetectors based on Type II InAs/GaSb/AlSb superlattices for very long wavelength infrared detection Binh-Minh Nguyen, Siamak Abdollahi Pour, Simeon Bogdanov, Manijeh Razeghi ∗ Center for Quantum Devices, Department of Electrical Engineering and Computer Science, Northwestern University, Evanston, Illinois 60208 ABSTRACT The bandstructure tunability of Type II antimonide-based superlattices has been significantly enhanced since the introduction of the M-structure superlattice, resulting in significant improvements of Type II superlattice infrared detectors. By using M-structure, we developed the pMp design, a novel infrared photodetector architecture that inherits the advantages of traditional photoconductive and photovoltaic devices. This minority electron unipolar device consists of an M-structure barrier layer blocking the transport of majority holes in a p-type semiconductor, resulting in an electrical transport due to minority carriers with low current density. Applied for the very long wavelength detection, at 77K, a 14μm cutoff detector exhibits a dark current 3.3 mA/cm 2 , a photoresponsivity of 1.4 A/W at 50mV bias and the associated shot-noise detectivity of 4x10 10 Jones. Keywords: Type II superlattice, InAs/GaSb, M-structure, pMp design, minority carriers, VLWIR. INTRODUCTION The idea of heterostructures was first discussed by H. Kroemer in the 1950s 1 and has gained a lot of attention from the semiconductor world. Many attempts have been made to profit from the advantages of heterostructures, i.e., to independently and separately control the distribution and flow of electrons/ holes within a semiconductor device. However, due to the limited number of available combinations of bulk semiconductors that are closely lattice matched, the band discontinuity of heterostructures has very poor tunability or is not changeable. It was not until the further development by L. Esaki et al in 1970s 2 with the concept of superlattices (SL) that the heterostructure technology could achieve greater flexibility in controlling the energy levels and band discontinuity. The superlattice is treated as an artificial bulk material with alternative heterojunctions at the atomic scale that create periodic local confinement of carriers and effective energy levels dependent on the constituent layer thicknesses. For example, in Type – II InAs/GaSb superlattice where electrons and holes are spatially separated into the InAs and GaSb wells respectively, it has been experimentally demonstrated that the effective bandgap of the material can be changed from 40meV to more than 400meV (3 to 30 μm) 3 and the energy bands can be optimized for the suppression of Auger recombination 4 . With these advantages, Type – II InAs/GaSb superlattice has rapidly emerged in the infrared detection technologies and becomes a rival competitor to the state-of-the-art Mercury Cadmium Telluride (MCT) technology. With the invention of more complex variants such as W-structure 5 , M-structure 6 , the band gap engineering capability of T2SLs have become even more flexible, with the full tailorability of both the conduction band and the valence band while keeping the lattice match conditions to ensure high crystalinity of the material 7 . In recent years, various designs based on T2SLs have drastically changed the architecture of infrared detectors. Among them, one can ∗ Corresponding author: email: razeghi@eecs.northwestern.edu Quantum Sensing and Nanophotonic Devices VII, edited by Manijeh Razeghi, Rengarajan Sudharsanan, Gail J. Brown, Proc. of SPIE Vol. 7608, 760825 · © 2010 SPIE · CCC code: 0277-786X/10/$18 · doi: 10.1117/12.855635 Proc. of SPIE Vol. 7608 760825-1