We present a high-performance short-wavelength infrared n-i-p photodiode, whose structure is based on type-II
superlattices with InAs/InAs1-xSbx/AlAs1-xSbx on GaSb substrate. At room temperature (300K) with front-side
illumination, the device shows the peak responsivity of 0.47 A/W at 1.6mm, corresponding to 37% quantum efficiency at
zero bias. At 300K, the device has a 50% cut-off wavelength of ~1.8mm. For −50mV applied bias at 300 K the
photodetector has dark current density of 9.6x10-5 A/cm2 and RxA of 285 Ω•cm2, and it revealed a detectivity of
6.45x1010 cm•Hz1/2/W. Dark current density reached to 1.3x10-8 A/cm2 at 200 K, with 36% quantum efficiency which
leads to the detectivity value of 5.66x1012 cm•Hz1/2/W.
We report InAs/InAs1-xSbx type-II superlattice base photodetector as high performance long-wavelength infrared nBn device grown on GaSb substrate. The device has 6 μm-thick absorption region, and shows optical performance with a peak responsivity of 4.47 A/W at 7.9 μm, which is corresponding to the quantum efficiency of 54% at a bias voltage of negative 90 mV, where no anti-reflection coating was used for front-side illumination. At 77K, the photodetector’s 50% cut-off wavelength was ~10 μm. The device shows the detectivity of 2.8x1011 cm.√Hz/W at 77 K, where RxA and dark current density were 119 Ω•cm2 and 4.4x10-4 A/cm2 , respectively, under -90 mV applied bias voltage.
Low-frequency noise has been studied in a mid-wavelength infrared InAs/GaSb type-II superlattice-based focal plane array. Low-frequency noise is observed under reverse bias but not at zero bias, even in the presence of photo-current. The magnitude of low-frequency noise was separately measured as a function of operating temperature and operation bias. The low-frequency noise is linearly correlated with the generation-recombination component of the dark current. No correlation of low-frequency noise with photo-current or diffusion dark current was found.
We report a bias selectable dual-band Type-II superlattice-based short-wave infrared (SWIR) and mid-wave infrared (MWIR) co-located photodetector capable of active and passive imaging. A new double-layer etch-stop scheme is introduced for back-side-illuminated photodetectors, which enhanced the external quantum efficiency both in the SWIR and MWIR spectral regions. Temperature-dependent dark current measurements of pixel-sized 27 μm detectors found the dark current density to be ~1×10-5 A/cm2 for the ∼4.2 μm cut-off MWIR channel at 140 K. This corresponded to a reasonable imager noise equivalent difference in temperature of ∼49 mK using F⁄2.3 optics and a 10 ms integration time (tint), which lowered to ∼13 mK at 110 K using and integration time of 30 ms, illustrating the potential for high-temperature operation. The SWIR channel was found to be limited by readout noise below 150 K. An excellent imagery from the dual-band imager exemplifying pixel coincidence is shown.
We report a bias selectable dual-band mid-wave infrared (MWIR) and long-wave infrared (LWIR) co-located detector with 3 μm active region thickness per channel that is highly selective and can perform under high operating temperatures for the MWIR band. Under back-side illumination, a temperature evolution study of the MWIR detector’s electro-optical performance found the 300 K background-limit with 2π field-of-view to be achieved below operating temperatures of 160 K, at which the temperature’s 50% cutoff wavelength was 5.2 μm. The measured current reached the system limit of 0.1 pA at 110 K for 30 μm pixel-sized diodes. At 77 K, where the LWIR channel operated with a 50% cutoff wavelength at 11.2 μm, an LWIR selectivity of ∼17% was achieved in the MWIR wave band between 3 and 4.7 μm, making the detector highly selective.
Active and passive imaging in a single camera based on the combination of short-wavelength and mid-wavelength
infrared detection is highly needed in a number of tracking and reconnaissance missions. Due to its versatility in
band-gap engineering, Type-II InAs/GaSb/AlSb superlattice has emerged as a candidate highly suitable for this
multi-spectral detection.
In this paper, we report the demonstration of high performance bias-selectable dual-band short-/mid-wavelength
infrared photodetectors based on InAs/GaSb/AlSb type-II superlattice with designed cut-off wavelengths of 2 μm
and 4 μm. Taking advantages of the high performance short-wavelength and mid-wavelength single color
photodetectors, back-to-back p-i-n-n-i-p photodiode structures were grown on GaSb substrate by molecular beam
epitaxy. At 150 K, the short-wave channel exhibited a quantum efficiency of 55%, a dark current density of 1.0x10-9 A/cm2 at -50 mV bias voltage, providing an associated shot noise detectivity of 3.0x1013 Jones. The mid-wavelength
channel exhibited a quantum efficiency of 33% and a dark current density of 2.6x10-5 A/cm2 at 300 mV bias voltage,
resulting in a detectivity of 4.0x1011 Jones. The operations of the two absorber channels are selectable by changing
the polarity of applied bias voltage.
Recently, the type-II InAs/GaSb superlattice (T2SL) material platform is considered as a potential alternative for
HgCdTe technology in long wavelength infrared (LWIR) imaging. This is due to the incredible growth in the
understanding of its material properties and improvement of device processing which leads to design and fabrication of
better devices. In this paper, we report electrical low frequency noise measurement on a high performance type-II
InAs/GaSb superlattice 1024×1024 LWIR focal plane array.
One of the biggest challenges of improving the electrical performance in Type II InAs/GaSb superlattice
photodetector is suppressing the surface leakage. Surface leakage screens important bulk dark current mechanisms,
and brings difficulty and uncertainty to the material optimization and bulk intrinsic parameters extraction such as
carrier lifetime and mobility. Most of surface treatments were attempted beyond the mid-infrared (MWIR) regime
because compared to the bulk performance, surface leakage in MWIR was generally considered to be a minor factor.
In this work, we show that below 150K, surface leakage still strongly affects the electrical performance of the very
high bulk performance p-π-M-n MWIR photon detectors. With gating technique, we can effectively eliminate the
surface leakage in a controllable manner. At 110K, the dark current density of a 4.7 μm cut-off gated photon diode is
more than 2 orders of magnitude lower than the current density in SiO2 passivated ungated diode. With a quantum
efficiency of 48%, the specific detecivity of gated diodes attains 2.5 x 1014 cmHz1/2/W, which is 3.6 times higher than
that of ungated diodes.
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