Research progress and development trends of antimonide-based superlattice infrared photodetectors

Significance  Infrared focal plane arrays (FPAs) are indispensable core components in many fields such as aerospace remote sensing, deep space exploration, national defense and security, resource exploration, and industrial control. In recent years, the antimonide-based superlattice is drawing the research interests from all over the world. It has become the prominent candidate to achieve infrared detectors with high-uniform large arrays, extended detection wavelengths to long wave and very long wave, two-color detection and so forth, due to its excellent uniformity, low dark current, relatively high quantum efficiency as well as the tunable detection wavelengths which almost covers the full infrared wavebands from near-infrared (NIR) to very long wave infrared (VLWIR). The basic technical principles of the antimonide-based superlattice for infrared detection, the several development stages and key results, as well as the development trends of the Type-II superlattice infrared focal plane arrays, are sequentially introduced and discussed. As antimonide-based superlattice evolves towards higher pixel density, larger specifications, higher operating temperature, longer detecting wavelength, two-color (multi-color), avalanche devices, it is depicted that the antimonide-based superlattice will always play an important role in many fields especially for infrared sensing and imaging.

Progress The development process of antimonide-based superlattice focal plane detectors is divided into three stages. The first stage spans from 1980s to the very beginning of 21^st century. This stage includes the proposal of the concept of superlattice infrared detection technology, theoretical calculation and analysis of the performance of superlattice detectors, epitaxial growth of superlattice materials (first MBE growth by HRL), and some preliminary research on basic optoelectronic properties. The research results of this stage demonstrate the decent capabilities of superlattice materials for infrared detection. The second stage spans from the very beginning of 21^st century to year about 2010. This stage mainly focuses on breakthroughs in key technologies for the preparation of high-performance focal plane devices. Particularly, the advanced heterostructures are studied and prepared to suppress the dark current of superlattice long-wavelength detectors. And the etching and sidewall passivation technologies of superlattice materials are explored to prepare superlattice FPA devices. Through these technical breakthroughs, FPAs with 1024 pixel×1024 pixel (Tab.1) and detecting wavelength longer than 10 μm are achieved. The third stage starts from about 2010 and until now. This stage is mainly about the improvement of superlattice focal plane preparation capabilities and the realization of engineering applications, and government becomes an important strength which quickly and efficiently promotes the developments of superlattice technologies. Under the support of related government agencies, Western countries with more technological accumulation make breakthroughs in key technologies such as superlattice structure design, material growth, and chip preparation processes. The VISTA project dominated by American government is a typical case with successful results and deep influence. FPAs with millions of pixels (up to 6 K×4 K), pixel pitches of less than 10 micrometers (e.g. ~5 μm), operating temperature as high as ~180 K are reported. Such superlattice FPAs have already been used in super transport aircrafts, the International Space Station (Fig.7), hyperspectral equipment and so forth.

Conclusions and Prospects  Since the idea of InAs/GaSb superlattice infrared detector was first proposed, it has been over 30 years during which domestic and foreign researchers have successively obtained a series of infrared detectors with large array, high temperature operation, long wave/multi-color detection, through structural design optimization and preparation technology improvement. Antimonide-based superlattice FPAs show advantages such as high uniformity, high stability, and high preparation controllability, and are widely used in aerospace fields such as infrared remote sensing and imaging. Now, to fabricate detectors with higher performance, higher requirements for superlattice materials are put forward. Essentially, materials with longer minor carrier lifetime, higher quantum efficiency and novel structure are explored. Based on the deeper studies, superlattice infrared focal planes are practically developing towards higher pixel density, larger specifications, higher operating temperature, longer detecting wavelength, two-color (multi-color) detection, avalanche devices, etc.