Broadband Ge/SiGe quantum dot photodetector on pseudosubstrate
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Broadband Ge/SiGe quantum dot photodetector on pseudosubstrate Andrew Yakimov* , Victor Kirienko, Vladislav Armbrister and Anatolii Dvurechenskii Abstract We report the fabrication and characterization of a ten-period Ge quantum dot photodetector grown on SiGe pseudosubstrate. The detector exhibits tunable photoresponse in both 3- to 5-μm and 8- to 12-μm spectral regions with responsivity values up to about 1 mA/W at a bias of −3 V and operates under normal incidence radiation with background limited performance at 100 K. The relative response in the mid- and long-wave atmospheric windows could be controlled through the applied voltage. Keywords: Quantum dots, Silicon, Germanium, Interband transitions, Infrared photodetectors
Background There is an increasing need for sources and detectors for mid-infrared (IR) spectral region due to the broad range of medical and industrial applications such as measurement of skin temperature, detection of cancer or infection, air pollution monitoring, meteorological research, and remote temperature sensing. Quantum well infrared photodetectors (QWIPs) utilizing intersubband transitions have been successful in these applications [1]. The intersubband transition energy in the quantum well is easily tunable by varying the quantum well width and barrier height. Also, there is a potential for the fabrication of uniform detector arrays with large area. However, QWIPs have drawbacks such as intrinsic insensitivity to the normal incidence radiation and a relatively large dark current. In the past several years, there has been a surge of interest in nanostructures that exhibit quantum confinement in three dimensions, which are known as quantum dots (QDs). With respect to quantum wells, the additional in-plane confinement of carriers and the peaked density of states in QDs lead to attractive properties in the mid-wave (3 to 5 μm) and long-wave (8 to 12 μm) IR regions where the Earth’s atmosphere has its major transmission windows [2]. The potential advantages of the
*Correspondence: [email protected] Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, Prospekt Lavrent’eva 13, Novosibirsk 630090, Russia
quantum dot infrared photodetectors (QDIPs) as compared with two-dimensional systems are the following [3,4]: (1) increased sensitivity to normally incident radiation as a result of breaking of the polarization selection rules, so eliminating the need for reflectors, gratings, or optocouplers, (2) expected large photoelectric gain associated with a reduced capture probability of photoexcited carriers due to suppression of electron-phonon scattering, and (3) small thermal generation rate, resulting from zero-dimensional character of the electronic spectrum, that renders a much improved signal-to-noise ratio. Most of the demonstrations of QDIPs were achieved with III-V self-assembled heterostuctures. SiGe-based QDIPs represent another attractive type of the device due to its compatibility with the standard Si reado
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