Recently, quantum dot infrared photodetectors (QDIP) have been intensively investigated because they can be
fabricated by conventional matured GaAs processing. QDIP can detect normal incident light in contrast to quantum well
infrared photodetectors (QWIP) which need optical grating or reflector. Also QDIPs operate at higher temperature,
taking advantage of their lower dark current theoretically than that of QWIPs.
In this report, we describe our effort to realize long-wavelength infrared (LWIR) QDIP infrared focal plane array
(IRFPA), which uses molecular beam epitaxially grown self-assembled quantum dot (SAQD) multilayers. We have
successfully "engineered" the transition levels of SAQDs to LWIR (8-12 μm) energy region, where relatively lower
quantum levels were pushed up near the conduction band edge of AlGaAs intermediate layers. In addition, these SAQD
multilayers bring QDIP responsivity enhancement due to their higher dot density.
We applied this structure to 256×256 pixel LWIR QDIP IRFPA. As a result, we realized the response peak
wavelength of 10 μm and noise equivalent temperature difference of our newly developed QDIP was 87 mK at 80 K, 120
Hz frame rate with f/2.5 optics. We obtained the excellent quality of IR image and confirmed our QDIP's high sensitivity
and high speed operation.