Infrared photodetectors can be applied to a wide range of applications, including free-space communication, surveillance, chemical sensing, and biomedical imaging. Third generation infrared imaging systems of high performance are in high demand to meet the requirements of various applications from defence to civil sections.
The state-of-the-art CdHgTe (CMT) photodetectors are currently dominating the infrared market due to the near ideal properties for infrared sensing as well as well-established fabrication techniques in the last 50 years. Nonetheless, the CMT technology suffers from very high cost and difficulty to obtain large-format arrays.
In the last two decades, quantum structured infrared photodetectors based on III-V materials have attracted a lot of attention to realise the third generation infrared photodetectors. Both single pixels and focal plane arrays of detectors with promising performance have been demonstrated. However, CMT detectors are yet to be challenged by the new technologies in terms of efficiency and noise. At UCL, we aim to developing high-performance infrared photodetectors based on semiconductor nanostructures, including QDs, type II superlattices, and nanowires. Additionally, in order to take the advantage of mature Si technology, monolithically integrated infrared photodetectors are under development at UCL to realise higher performance, enhanced functionality, and higher resolution focal plane arrays but cost-effective at the same time. Recently, the first InAs/GaAs quantum dot infrared photodetector directly grown on Si substrates have been developed at UCL (Fig. 1).
Figure 1. A high quality QDIP directly grown on a Si substrate with mid-infrared photoresponse peaked at ~ 7 µm. Copyright © 2016 American Chemical Society .
 Jiang Wu; Qi Jiang; Siming Chen; Mingchu Tang; Yuriy I. Mazur; Yurii Maidaniuk; Mourad Benamara; Mykhaylo P. Semtsiv; W. Ted Masselink; Kimberly A. Sablon; Gregory J. Salamo; Huiyun Liu; ACS Photonics 2016, 3, 749-753.