Quantum well infrared photodetectors (QWIPs) based on GaAs have attracted much attention owing to its matured material growth technique. In order to obey the selection rule of polarization, various grating structures have been attached to planar QWIPs. Recently, we experimentally demonstrated that strained planar QWIPs could be self-rolled up into an out-of-plane tubular geometry so that the polarization selection rule is sufficiently subdued without any extra grating structure. Such self-rolled-up QWIPs show a broadband enhancement of responsivity and detectivity over a wide incident angle. In this paper, both wave-optics and ray-optics simulations are performed to clarify the underlying physics. The well-defined curved QWIPs pave a path towards flexible QWIPs for flexible optoelectronics.
The design of quantum dot infrared photodetector (QDIP) based on metal-insulator-metal (MIM) microcavity in which the quantum dot (QD) is sandwiched between a planar metallic film and a metallic stripe is reported. By a finite difference time-domain (FDTD) method, the light coupling efficiency spectra and enhancement factor are numerically calculated. The results exhibit that the total electric field concentrated in metal-metal region is strongly enhanced when the resonant frequency of microcavity is equal to the QD’s peak response frequency. This enhancement effect mainly originates from the resonant coupling of incident photons into microcavity forming the surface plasmonic mode. The optimization of structural parameters for MIM microcavity is discussed, demonstrating an optimal structure of quantum dot infrared photodetector with the coupling efficiency improved nearly 7 times compared with conventional mesa QDIPs. So, it is deduced that a favorable performance of device such as high quantum efficiency and infrared responsivity is possible. Finally, the detector shows the potential application in the infrared sensing and imaging, as well as integrating with other electronic and optoelectronic device for the sub-wavelength size.
Near infrared light emitting diodes (LEDs) play an important role in infrared photodetectors; however, external quantum efficiency of GaAs LEDs is greatly confined as a result of critical angle and Fresnel diffraction. In this study, polystyrene spheres are used to fabricate photonic crystal. A ring-shaped ohmic contact was introduced to the device, and the current-voltage curves and light emitting efficiency were measured to characterize the property of device. The LED device with surface nano-structure exhibited better external quantum efficiency (EQE) and improved light extraction efficiency (LEE) in near infrared light emitting area compared to non-structure device.