With optimized buffer design, we demonstrate a new InAs/AlSb resonant tunneling diode (RTD) on lattice-unmatched semi-insulating (SI) GaAs (100) substrates aiming for terahertz oscillators. To obtain high crystal quality and smooth surface, 5 periods InGaAs/GaAs (2ML/2ML) superlattices (SLs) buffer layer was used as dislocation filters (DFs). Xray diffraction (XRD) measurement showed the full width at half maximum (FWHM) of 331arcsec and surface roughness of 2.4nm over 10μm×10μm. 8-μm-diam diodes were fabricated by standard mesa process. I-V characteristic of the diodes shows negative conductivity at room temperature and a peak current density of 1.79×105A • cm-2 was achieved.
In this work, we report a separate absorption and multiplication avalanche photodiode (SAM-APD) with 100% cut-off wavelength of ~2.1 μm at 300 K grown by molecular beam epitaxy. The electron-dominated avalanche mechanism multiplication region was designed as a multi-quantum well structure consisting of AlAsSb/GaSb H-structure superlattice and Al0.3In0.7AsSb digital alloy. At room temperature, the device exhibits a maximum multiplication gain of 79 under -13.3 bias voltage.
We report cylinder photon traps, prism photon traps, and SiO2/Ta2O5 antireflection films added to the active areas of short wavelength infrared detectors. The total device thickness was estimated ~3.3μm and with the p-i-n structure based on antimonide. The simulation results show that the photon traps increase the absorption of the invisible spectrum distinctly. Also, the optical measurements reveal that maximal responsivity of the detector with PTs array is 0.094A/W in the visible range and 0.64A/W in the short wavelength infrared spectrum. The responsivity in the wavelength of short-wave infrared can be increased apparently as well. Thus, the photon traps array may a potential method for antimonide-based visible to short wavelength infrared bispectral photodetector.
In this paper, a mid-/long-wave dual-band detector with N-M-π-B-π-N sturcture was developed based on type-II InAs/GaSb superlattice was fabricated by adopting the dual-band structure. The dual-band detector epi-layer presented high crystalline quality of epi-layers. The two channels, with respective 50% cut-off wavelength at 3.5 μm and 11.8 μm were obtained. The peak quantum efficiency (QE) of mid wavelength infrared (MWIR) band and long wavelength infrared (LWIR) band were 22% at 2.7 μm under no bias voltage and 23% at 9.1 μm under -180 mV, respectively. The resistance under 0 and -180 mV of applied bias were 1.7×104 Ω·cm2 and 97 Ω·cm2. Due to the high resistance of long wavelength infrared channel, the specific detectivity of LWIR band maintains above 1011 cm·Hz1/2/W from 4.5 μm to 12.6 μm under - 180 mV at 77K. Finally, the thermal images of both channel were taken by the fabricated FPA.
Near-infrared InAs/GaSb Type-Ⅱ superlattices is widely used in biomimetics, sensing, color-imaging technology and other applications. An antireflection coating(AR coating) can help it perform better, making the infrared photodetector a higher responstivity and also a higher quantum efficiency. We produce a broadband AR coating by plasma-enhanced chemical vapor deposition(PECVD) then using the lift-off technology making no damage without any change in the usual Infrared detector process flow, a 260 nm SiO2 AR coating is transform onto the surface of the infrared photodetector. After using the AR coating, the antireflection can provide up to 40% light gain, while the average reflectivity of the surface of InAs/GaSb type-Ⅱ superlattice is decreased from 33% to 14%. The responsitivity is increased obviously.
We report three kinds of surface passivation for AlxInyAsSb APD, which are SiO2, SiO2 after sulfuration and SU8 2005 treatments. A good sidewall profile of mesas were etch by Inductively Coupled Plasma (ICP) to 2.6μm depth. The order of dark current for device with SU8 passivation is less than -12 under the temperature of 100K. Dark current and photocurrent increase linearly with diameter of mesa. Also, the devices with different passivation methods produce photocurrent excited by incident power. The measurements are consistent with CV modeling and electric field simulations.
High indium composition InxGa1-xAs/GaAs quantum wells (x˃0.4) in which the well width reached to 7 nm without relaxing were grown on (100) GaAs substrates by MBE. The good crystal quality and optical properties of the high strained InGaAs/GaAs QW were obtained by controlling quasi-2D growth model and optimizing the growth condition including the growth temperature, growth rate, and V/III BEP ratio. Photoluminescence (PL) showed that the cutoff wavelength was about 1.3μm at room temperature with narrow full width at half maximum below 30meV. Dilute nitrogen and high In composition InGaAsN/GaAs QW extended wavelength infrared photodetectors at 1.3 and 1.55 μm were also realized.
Optimization of growth parameters for type-II 17MLs InAs/8MLs GaSb strained layer superlattices (SLS)
(λcut-off~20 μm at 77K), grown on GaSb substrates by solid source molecular beam epitaxy (MBE), has been undertaken.
Both the GaSb on InAs interface and the InAs on GaSb interface were inserted with InSb interfaces using migration
enhanced epitaxy (MEE) method to balance the lattice mismatch. The influence of the effect of the thickness of InSb
layer on the properties of the superlattice has been investigated. We demonstrate the structural properties of these SLS
structures, using high-resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM) and high-resolution
transmission electron microscopy (TEM). Optimized growth parameters were then used to grow SLS detectors with the
active region of 2-μm-thick, which demonstrated full-width half-maximum (FWHM) of 22 arcsec for the first SLS
satellite peak and nearly zero lattice mismatch between zero-order SLS peak and GaSb substrate. The cut-off wavelength
of the detector is 20 μm at 77K measured by Fourier Transform Infrared (FTIR) spectrometer with the quantum
efficiency of 10% and the Johnson noise limited detectivity reached 2.8×1010 cm Hz1/2/W at 10.55μm under -75mV bias
voltage.
Since InAs/GaSb type-II superlattices (T2SL) were first proposed as infrared (IR) sensing materials, T2SL
mid-wave IR (MWIR) and long-wave IR (LWIR) are of great importance for a variety of civil and military applications.
A very important parameter of IR photodetectors is dark current, which affects the detectivity directly. Chemical and
physical passivation has revealed to be an efficient technique to reduce surface component of dark current, which will
become a dominant current in focal plane arrays (FPA). In this paper we talk about the electrochemistry and dielectric
method for passivation. We choose anodic sulfide and SiO2 passivation. The leakage current as a function of bias voltage
(I–V) results show dark current of anodic sulfide device was two orders of magnitude lower than unpassivation one, but
reactive magnetron sputtering SiO2 didn’t perform well. The highest R0A we get from the sulfurizing experiment is
657Ω·cm2 in 77K. After fabrication the measured cutoff wavelength is 5.0μm. Finally blackbody test result shows that
the peak quantum efficiency (QE) at 3.33μm is 68% and the peak detectivity is 7.16x1011cm·Hz1/2/W.
Recently excellent infrared detectors have been demonstrated using InAs/GaSb superlattice materials sensitive at wavelength from 3um to greater than 32um. Using empirical tight binding method (ETBM), different structures as InAs(xML)/GaSb(8ML), (x=2, 4, 6, 8) and InAs(14ML)/GaSb(7ML) were designed for various cut-off wavelengths from short to long IR wavelength. These materials were grown by MBE with valved cracker cells for arsenic and antimony on p-type GaSb(001) substrates. The microstructure and the bandgap Eg were verified by high resolution X-ray diffraction and photoresponse spectra. The temperature dependence of Eg and photoresponse responsivity Rv were studied. The differential resistance under zero bias R0 in MWIR photodiode was measured up to 106 ohms. The ideality factor in the range of 1.5 to 2.1 indicates the generation-recombination current and surface leakage current are the dominant leakage in the depletion region. These results will promote InAs/GaSb superlattices infrared detectors research in multi-color from short to long wave IR application.
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