We report on InGaAsSb infrared photodetector and light emitting diode for short wavelength infrared detection and emission. The InGaAsSb samples were grown by molecular beam epitaxy (MBE) system on a GaSb substrate. In order to investigate the structural properties of InGaAsSb layer, we took a high resolution XRD and low voltage SEM. The InGaAsSb devices were processed in 400×400 μm2 using inductively coupled plasma etching. We have measured the spectral response of InGaAsSb based photodetector using various temperature and bias. The cut-off wavelength of photodetector was 3.0 μm at room temperature. We also report an electroluminescence of InGaAsSb LED. Keywords: Short wavelength infrared, photodetector, light emitting diode, InGaAsSb, GaSb.
The plasmonic metamaterial perfect absorber (MPA) is a recently developed branch of metamaterial which exhibits nearly unity absorption within certain frequency range.[1-6] The optically thin MPA possesses characteristic features of angular-independence, high Q-factor and strong field localization that have inspired a wide range of applications including electromagnetic wave absorption,[3, 7, 8] spatial and spectral modulation of light, selective thermal emission, thermal detecting and refractive index sensing for gas and liquid[12, 13] targets. In this work, we demonstrate a MPA working at terahertz (THz) regime and characterize it using an ultrafast THz time-domain spectroscopy (THz-TDS). Our study reveal an ultra-thin Fabry-Perot cavity mechanism compared to the impedance matching mechanism widely adopted in previous study [1-6]. Our results also shows higher-order resonances when the cavities length increases. These higher order modes exhibits much larger Q-factor that can benefit potential sensing and imaging applications.
 C. M. Watts, X. L. Liu, and W. J. Padilla, "Metamaterial Electromagnetic Wave Absorbers," Advanced Materials, vol. 24, pp. 98-120, Jun 19 2012.
 M. Hedayati, F. Faupel, and M. Elbahri, "Review of Plasmonic Nanocomposite Metamaterial Absorber," Materials, vol. 7, pp. 1221-1248, 2014.
 N. I. Landy, S. Sajuyigbe, J. J. Mock, D. R. Smith, and W. J. Padilla, "Perfect metamaterial absorber," Physical Review Letters, vol. 100, p. 207402, May 23 2008.
 H. R. Seren, G. R. Keiser, L. Cao, J. Zhang, A. C. Strikwerda, K. Fan, et al., "Optically Modulated Multiband Terahertz Perfect Absorber," Advanced Optical Materials, vol. 2, pp. 1221-1226, 2014.
 D. Shrekenhamer, J. Montoya, S. Krishna, and W. J. Padilla, "Four-Color Metamaterial Absorber THz Spatial Light Modulator," Advanced Optical Materials, vol. 1, pp. 905-909, 2013.
 S. Savo, D. Shrekenhamer, and W. J. Padilla, "Liquid Crystal Metamaterial Absorber Spatial Light Modulator for THz Applications," Advanced Optical Materials, vol. 2, pp. 275-279, 2014.
 H. Tao, N. I. Landy, C. M. Bingham, X. Zhang, R. D. Averitt, and W. J. Padilla, "A metamaterial absorber for the terahertz regime: Design, fabrication and characterization," Optics Express, vol. 16, pp. 7181-7188, May 12 2008.
 J. Hao, J. Wang, X. Liu, W. J. Padilla, L. Zhou, and M. Qiu, "High performance optical absorber based on a plasmonic metamaterial," Applied Physics Letters, vol. 96, p. 251104, 2010.
 X. Liu, T. Tyler, T. Starr, A. F. Starr, N. M. Jokerst, and W. J. Padilla, "Taming the Blackbody with Infrared Metamaterials as Selective Thermal Emitters," Physical Review Letters, vol. 107, p. 045901, 07/18/ 2011.
 T. Maier and H. Brückl, "Wavelength-tunable microbolometers with metamaterial absorbers," Optics Letters, vol. 34, pp. 3012-3014, 2009/10/01 2009.
 A. Tittl, P. Mai, R. Taubert, D. Dregely, N. Liu, and H. Giessen, "Palladium-Based Plasmonic Perfect Absorber in the Visible Wavelength Range and Its Application to Hydrogen Sensing," Nano Letters, vol. 11, pp. 4366-4369, 2011/10/12 2011.
 N. Liu, M. Mesch, T. Weiss, M. Hentschel, and H. Giessen, "Infrared Perfect Absorber and Its Application As Plasmonic Sensor," Nano Letters, vol. 10, pp. 2342-2348, Jul 2010.
 G. H. Li, X. S. Chen, O. P. Li, C. X. Shao, Y. Jiang, L. J. Huang, et al., "A novel plasmonic resonance sensor based on an infrared perfect absorber," Journal of Physics D-Applied Physics, vol. 45, p. 205102, May 23 2012.
We report on InAs SML QD infrared photodetector performance for long wavelength infrared detection. The device
structure consists of InAs SML QDs embedded in InxGa1-xAs quantum well (QW) surrounded by GaAs and AlxGa1-
xAs barrier. In order to investigate the structural properties of SML QDs, we took cross-sectional STEM images. We
have measured the polarization dependent spectral response of SML-QD based photodetector using various angular inplane
and out-plane polarizations. We also report a systematic approach for controlling the intersubband transition
energy level in SML QD infrared photodetectors, in order to control the peak wavelength of the device.
Metallic metamaterial structures are used in nanophotonics applications in order to localize and enhance an incident
electromagnetic field. We have theoretically and experimentally studied resonant coupling between plasmonic modes of
an SRR array and a quantum dot-in-a-well (DWELL) heterostructure. The near-field distribution from the SRRs on the
GaAs substrate was first modeled by electromagnetic simulations and optimized SRR dimensions for maximum nearfield
coupling at the peak absorption were extracted. The DWELL sample with a ground state emission peak at 1240 nm
was grown by molecular beam epitaxy on a semi-insulating GaAs substrate. The sample was uniformly covered with an
array of SRRs, and patterned by standard electron-beam-lithography. In order to study the near field coupling of the
plasmonic structure into the DWELL, optical characterization was performed on the SRR-DWELL heterostructure,
including room temperature photoluminescence, and transmission measurement.
Detectivity of mid-wave infrared (MWIR) detectors based on InAs/GaSb type II strained layer superlattices (T2SLs) can be significantly enhanced at select wavelengths by integrating the detector with a back-side illuminated plasmonic coupler. The application of a simple metal-T2SL structure directly on the GaSb substrate can result in radiation losses into the substrate due to the low refractive index of T2SL layer. However, insertion of a higher refractive index material, such as germanium (Ge), into the metal-SLS structure can confine the surface plasmon waveguide (SPW) modes to the surface. In this work, metal (Au)-Ge-T2SL structures are designed with an approximately 100 nm thick Ge layer. The T2SL layer utilized a p-i-n detector design with 8 monolayers (MLs) InAs/8 MLs GaSb. A plasmonic coupler was then realized inside the 300 μm circular apertures of these single element detectors by the formation of a corrugated metal (Au) surface. The T2SL single element detector integrated with an optimized plasmonic coupler design increased the quantum efficiency (QE) by a factor of three at an operating temperature of 77 K and 3 to 5 μm illumination wavelength, compared to a reference detector structure, and each structure exhibited the same level of dark current.
Current infrared imaging systems monitor emission from a given scene over a broad spectral range, which results with "black and white" images. As a result, there is ever increasing emphasis on the development of new, on the pixel level, infrared imaging technology that can provide spectral information. Attempts at creating a robust imaging system with spectral information have been made through a network of external optics, which results with a high cost and large system package. Here, we propose a metamaterial design that resonantly couples to an infrared photodetector for enhanced performance.
We have investigated optical properties and figures of merit of sub-monolayer quantum dots (SML-QD) infrared
photodetector and compared them with conventional Stranski-Krastanov quantum dots (SK-QD) with a similar design.
The purpose of this study is to examine the effects of varying the number of stacks(2,3,4,5 and 6) in SML-QD detector
on its device performance The peak of photoluminescence (PL) spectra of SK-QD and SML-QDs are observed at
1.07eV and 1.24~1.35eV at room temperature, respectively. The PL peak of 2 and 3 stacks SML QD are very close to
the GaAs band edge peak (1.42eV) and the full width at half maximum (FWHM) of all the SML-QD are much narrower
than SK-QD. Normal incidence photoresponse peak of 4 stacks SML QDIP are obtained at 7.5μm with responsivity of
0.5 A/W and detectivity of 1.2×10<sup>11</sup> cm.Hz<sup>1/2</sup>/W (77K, 0.4V, f/2 optics), which is much narrower than spectral response
of SK QDIP possibly due to bound-to-bound transition.
Systematic characterization of various types of intersubband transitions in the quantum dots in a well
(DWELL) infrared photodetectors has been presented. By changing the thickness of the quantum well,
the excited state energy can be tuned with respect to the barrier, without altering the quantum dot
ground state. Bound to continuum transitions offer very high extraction probability for photoexcited
electrons but poor absorption coefficient, while the bound to bound transitions have higher absorption
but poorer extraction probability. Bound to quasibound transition is optimum for intermediate values
of electric fields with superior signal to noise ratio. The bound to quasibound device has the detectivity
of 4×10<sup>11</sup> cm.Hz<sup>1/2</sup> W<sup>-1</sup> (+3V, f /2 optics) at 77 K and 7.4×10<sup>8</sup> cm.Hz<sup>1/2</sup> W<sup>-1</sup> at 200 K, which is highest
reported detectivity at 200 K for detector with long wave cutoff wavelength. High performance focal
plane arrays have been fabricated with noise equivalent temperature difference of 44 mK at 80 K for
6.1μm peak wavelength.