Quantum wells to quantum dots: 640x512 pixels Long-Wavelength Infrared (LWIR) Quantum Dot Infrared Photodetector (QDIP) imaging focal plane array

Abstract

We have exploited the artificial atom-like properties of epitaxially grown self-assembled quantum dots (QDs) for the development of high operating temperature long wavelength infrared (LWIR) focal plane arrays (FPAs). QD infrared photodetectors (QDIPs) are expected to outperform quantum well infrared detectors (QWIPs) and are expected to offer significant advantages over II-VI material based FPAs. We have used molecular beam epitaxy (MBE) technology to grow multi-layer LWIR Dot-in-a-Well (DWELL) structures based on the InAs/InGaAs/GaAs material system. This hybrid quantum dot/quantum well device offers additional control in wavelength tuning via control of dot-size and/or quantum well sizes. DWELL QDIPs were also experimentally shown to absorb both 45o and normally incident light. Thus we have employed a reflection grating structure to further enhance the quantum efficiency. The most recent devices exhibit peak responsivity out to 8.1 microns. Peak detectivity of the 8.1 µm devices has reached ~ 1 x 1010 Jones at 77 K. Furthermore, we have fabricated the first long-wavelength 640x512 pixels QDIP imaging FPA. This QDIP FPA has produced excellent infrared imagery with noise equivalent temperature difference of 40 mK at 60K operating temperature.