Nanoscale quantum dot infrared sensors with photonic crystal cavity

Abstract

We report high performance infrared sensors that are based on intersubband transitions in nanoscale self-assembled quantum dots combined with a microcavity resonator made with a high-index-contrast two-dimensional photonic crystal. The addition of the photonic crystal cavity increases the photocurrent, conversion efficiency, and the signal to noise ratio ͑represented by the specific detectivity D * ͒ by more than an order of magnitude. The conversion efficiency of the detector at V b = −2.6 V increased from 7.5% for the control sample to 95% in the PhC detector. In principle, these photonic crystal resonators are technology agnostic and can be directly integrated into the manufacturing of present day infrared sensors using existing lithographic tools in the fabrication facility. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2194167͔ Infrared sensors in the wavelength range of 3 -25 m are of immense technological importance due to their application in medical diagnostics, fire-fighting equipment, and night vision systems. Quantum dot infrared photodetectors have been identified as an emerging technology for this wavelength regime due to their low dark current leading to a potentially higher operating temperature and normal incidence operation based on a mature GaAs technology. [1][2][3][4][5] Presently, high performance midinfrared detectors are based on mercury cadmium telluride ͑MCT͒. Due to a dramatic change of the band gap as a function of material composition, it is very challenging to reproducibly obtain large area homogeneous materials suitable for large area focal plane arrays ͑FPA͒ based on this material system. In contrast, mature materials growth technologies for III-V semiconductors can provide very accurate control of compositions and homogeneity. Therefore there is interest in developing IR photodetectors using III-V materials. One of the most promising III-V semiconductor long wavelenght infrared ͑LWIR͒ detectors is the quantum well infrared photodetector ͑QWIP͒, 6-9 which employs the intersubband or the subbandto-continuum transitions in quantum wells. One of the drawbacks of n-type QWIPs is that they cannot detect normally incident light due to the restriction of selection rules for the optical transition. In contrast, the intersubband optical transitions in quantum dots ͑QDs͒ do not have that restriction, due to the three-dimensional quantum confinement. Theoretically, quantum dot infrared photodetectors ͑QDIPs͒ and quantum dot-in well ͑DWELL͒ detectors ͑which is a combination of a quantum dot and quantum well detector͒ offer several advantages over QWIPs, including lower dark current ͑hence higher T operation͒, higher responsivity, normal incidence detection, and improved radiation hardness. 10,11 QDIPs with low dark current densities and high operating temperature have been reported. 2,3 Asymmetrically designed DWELL detectors have also been shown to have a biasdependent spectral response that is suitable for multispectral imagery. 12 Recently, a two color 320ϫ 256 FPA, based on a volt...

Ultra-subwavelength phase-sensitive Fano-imaging of localized photonic modes

“…For example, photon tunneling in coupled photonic crystal nanocavities (PCNs) is governed by the electric LDOS spatial overlap between neighboring resonators 8 . Similarly, the electric LDOS of a localized mode strongly influences the light-matter interaction of a single quantum emitter (being directly related to the spontaneous emission rate 9 as well as to the signal amplification 10 ), and the electric LDOS is crucial for the development of efficient sensors 11,12 . Major advances in tailoring the electric LDOS at the nanoscale have led, on one hand, to a sub-wavelength electric field confinement in metallic nanoantennas to control the directional emission 13 and, on the other hand, to the achievement of the strong coupling regime, with the requirement of placing the wavelength-matched nano-emitter at the location of the maximum of the PCN electric LDOS at a spatial precision of approximately l/15 14 .…”

Spectrally selective infrared absorption in defect-mode photonic-crystal-slab cavity

“…Most of the work so far has been focused on the absorption change in one-dimensional distributed Bragg reflector (1D DBR) based cavities [12,20], or one-, two-and three-dimensional (1D, 2D, 3D) metallic photonic crystal cavities [11,13,17]. Little work has been reported on the modified absorption characteristics in 2D dielectric photonic crystal slab (PCS) cavities [14], to the best of our knowledge.…”

“…Enhanced absorption can happen near or at the band edge where the electromagnetic Bloch wave is still extended throughout the structure, its group velocity is near zero, and the photonic DOS is greatly increased. In this regime, enhanced light-matter interaction is expected, and enhanced laser gain, light absorption and nonlinear effects have all been proposed [2,[11][12][13][14][15][16][17]. Enhanced absorption in tungsten 3D PCs has been reported [18].…”

“…quantum well, quantum dots) can lead to the modification of the absorption characteristics, due to the spectrallyselective light-matter interaction in the cavity. We propose a photonic crystal infrared Page 2 photodetector (PCIP) configuration, where the photonic crystal defect cavity was integrated with the quantum dot infrared photodetectors (QDIPs) [14,21] for higher operation temperature and spectrally selective absorption, highly desirable for infrared gas sensing and hyper-spectral imaging. High spectral selectivity with tunable wavelength coverage and spectral width can be feasible based on defect engineering and simple lithographic control, and/or external control [22].…”

Comparison studies of infrared photodetectors with a quantum-dot and a quantum-wire base

“…It is assumed that the QDIP active region is lightly doped by donors. The quantum−dot infrared photo− detector has emerged as an interesting and potentially viable device, wherein three−dimensional quantum confinement promises low dark currents [12,13], leading to a large detec− tivity [7]. We focus on QDIPs with multiple QD arrays of large−size QDs.…”