The polarization-integrated infrared detector (PIID) can distinguish the intrinsic property polarization of artificial target and background, and improve the capability of target detection and recognition. In this paper, we use the finite element method (FEM) to build the physical model of long wavelength (LWIR) PIID (8-14um) detector based on InAs/GaSb II superlattices (T2SLs). Our calculation results show thate grating array period, grating line width and thickness can effectively influence the light crosstalk between adjacent pixels, which is the key to the device extinction ratio. In addition, we design micro-structure to PIID, which plays an important role in improving device extinction. As a result, the extinction ratio was improved from 75:1 to 610:1 at the wavelength of 10.9μm. The physical mechanism of suppressing extinction ratio is analyzed in detail.
In this work, we report interband cascade light emitting diodes (ICLEDs) based on InAs/GaAsSb superlattices emitting around 4.5 μm The ICLED structures were grown on InAs substrates by molecular beam epitaxy, which were composed of InAs/GaAsSb superlattice emitters, InAs/AlAsSb multi-quantum well (MQW) injection regions, and the GaAsSb/AlAsSb MQW tunneling regions. Both 5-stage and 2-stage ICLEDs were fabricated. The devices exhibited high output power, low series resistance and high wall-plug efficiency (WPE). At room temperature, radiances of 0.36 W/cm2 sr and 0.19 W/cm2 sr were achieved from the 5-stage and 2-stage ICLEDs respectively. At 80 K, the output power from the 5-stage ICLED reached 3.56 mW with 350 mA injection current, resulting in a WPE of around 0.5%. The efficiency was largely maintained with increasing injection. The thermal quenching of these ICLEDs from 20 K to 300 K was also significantly less than other types of devices emitting at similar wavelengths. These results demonstrate that ICLEDs have great potential for mid-infrared light emitting diode applications requiring large output power and high wall-plug efficiency.
Many applications such as toxic gas detection or H2S monitoring in natural gas require operation in the THz spectral region, where gas species show distinct spectral “fingerprints” that can be easily discriminated by the gas matrix background absorption features.
So far, continuous-wave THz quantum cascade lasers employed in quartz-enhanced photoacoustic (QEPAS) sensors required liquid helium-cooling systems. In this work, we demonstrated the first liquid nitrogen-cooled THz QEPAS sensor for H2S detection operated in pulsed mode and mounting a spectrophone based on a quartz tuning fork with 1.5 mm prong spacing. A sensitivity level in the part-per-billion concentration range was achieved.
The polarization-integrated infrared detector (PIID) can effectively improve the detection and recognition ability of the target by utilizing the significant difference in polarization between the artificial target and the natural background. However, the existing PIID generally has a problem that the light crosstalk between adjacent pixels is relatively high, as a result, the polarization extinction ratio is lowered. In this paper, we use the finite element method (FEM) to build the physical model of PIID (3-5um) detector based on InAs/GaSb II superlattices (T2SLs) and simulate the influence of varied grating parameters (array period, line width, thickness, metal materials, etc.), channel passivation layer, substrate thickness and pixel size on the light crosstalk of adjacent pixels under front and back illumination. The calculation results show that reducing the grating array period, increasing the grating line width and thickness, increasing the pixel size, reducing the substrate thickness and the channel width can effectively suppress the light crosstalk between adjacent pixels and improve the device extinction ratio. However, increasing the polarization extinction ratio brings the problem of reducing the quantum efficiency of the device. Integrated optical design of our follow-up work in this paper such as reflection film, anti-reflection film, and light field control in different functional areas of the device is being considered. PIID with high extinction ratio and high quantum efficiency can be simultaneously obtained by electron beam lithography.
The requirement of the infrared technology applied on meteorological satellites is the key driving force for the development of infrared technology in Shanghai institute of technical physics (SITP), Chinese Academy of Sciences. The meteorological satellites have become a main detection method for the weather and ocean observation, there are totally 15 meteorological satellites that were launched into both sun synchronous and geostationary orbit and more satellites are under construction to be the second generation ones. The infrared remote sensors are the main payloads on-board on all these satellites. By these infrared remote sensors one can obtain the remote sensing data for ocean colour, water vapour, weather forecasting, and get the atmospheric temperature profile and humidity profile, etc. As the key technology in the infrared remote sensor, the infrared detector technology is developed mainly using the HgCdTe material, meanwhile the quantum well infrared photodetector and type II super-lattice infrared detector are also developed.
We report on a p-i-n photodetector based on type II InGaAs/GaAsSb SLs with a cutoff wavelength of 2.5 μm at room temperature. High quality materials were grown on an n-type (100) InP substrate by molecular beam epitaxy. Photoluminescence spectroscopy peak of the SLs around 2.5 μm and atomic steps in the atomic force microscope image were clearly observed. A device with the 100% cutoff wavelength of 2.5 μm at 293 K was fabricated. Temperature-dependent current-voltage measurements show that the diffusion current and generation-recombination current dominate at temperatures higher than 200 K while the generation-recombination current and trap-assisted tunneling current dominate at temperatures below 200 K. The optical response measurement quantum efficiency increases with reverse bias, and a diffusion length of 0.3 μm was extracted. The cause of the small diffusion length and possible approaches to improve it were briefly discussed.
As a promising candidate for the next generation of infrared detection and imaging, more and more studies are focused on the type-II InAs/GaSb superlattice recently. In this paper, we studied different passivation techniques and the dielectric film-semiconductor interface properties for InAs/GaSb superlattice photodetectors. We found that with Si3N4 passivation, the R0A of the superlattice detector decreased from 2.8×105Ωcm2 to 12Ωcm2 at 80K after a process of rapid thermal annealing (RTA) at 250°C for 60s. Excessive surface charge of 6.15×1012cm-2 was measured from a gate-controlled structure. Meanwhile, the SiO2 passivated devices can sustain its electrical performance after the RTA process.
In this paper, our recent study on InGaAs/GaAsSb Type II photodetector for extended short wavelength infrared detection is reported. The high quality InGaAs/GaAsSb superlattices (SLs) was grown successfully by molecular beam epitaxy. The full width of half maximum of the SLs peak is 39”. Its optical properties were characterized by photoluminescence (PL) at different temperature. The dependences of peak energy on temperature were measured and analyzed. The photodetector with InGaAs/GaAsSb absorption regions has a Quantum Efficiency (QE) product of 12.51% at 2.1um and the 100% cutoff wavelength is at 2.5um, at 300K under zero bias. The dominant mechanism of the dark current is discussed.
In recent years, interband cascade detectors (ICIP) based on typer-II superlattice have shown great performance potential at high operation temperature. In this paper, we report our studies on mid-infrared interband cascade photodetectors first grown on InAs substrate. We examined the photo-generated carriers’ transport in ICIP structures by comparing three detectors grown on InAs substrate. The 2-stages ICIP device has demonstrated a high quantum efficiency around 20% at room temperature. The dark current density of the 2-stages ICIP device at -0.05V is as low as 1 nA at 80K, 1 mA at 150K, which is comparable to the state of art PIN superlattice photodetectors with similar cutoff wavelength. The Johnson-noise limited D* reaches 1.64×1014cm.Hz1/2/W at 3.65 μm and 80K, and 4.1×1010cm.Hz1/2/W at 3.8 μm and 200K. The 300 K background limited infrared performance (BLIP) operation temperature is estimated to be over 140 K.
We report on the performance of long wavelength infrared type-II InAs-based InAs/GaAsSb superlattice photodiodes grown by molecular-beam epitaxy. The detectors had a 100% cutoff wavelength of ~ 9.7 μm and a peak current responsivity of 2.16 A/W at 80 K. The dark current density at -50 mV bias was 6.4×10-4 A/cm2 and the resistance-area product at zero bias (R0A) was 36.9 Ωcm2. The black body detectivity and peak detectivity were 7.5×1010 cm Hz1/2/W and 1.97×1011 cm Hz1/2/W, respectively. The quantum efficiency at 7.6 μm was measured to be ~34%. Good agreement was achieved between the measured I-V curves and the simulated ones, and between the experimental and theoretically predicted differential resistance values. At temperatures exceeding 75 K diffusion currents dominate the device performance. In the temperature range between 65 and 75 K, the performance of the InAs-based SL photodiodes is limited by GR processes. Trap-assisted tunneling current provides a significant contribution at temperatures below 65 K, while coherent tunneling currents are not of importance.
The barrier enhanced InAs/GaSb long wavelength photodetectors were proved to have better performance. Our previous work showed a PBIN detector with an electron barrier inserted show significantly improved electrical performances compared to a PIN structure. To improve the quantum efficiency, Be-doping was employed to convert the conductivity of the long wavelength SL structure, the PN junction moves away from the B-I hetrostructure to the π-N interface which loses the barrier effect. Therefore, the hole barrier was needed to form a PBπBN structure. In this paper, both the abrupt and gradual hole barrier was designed without Al element to form a PBπBN structure. The gradual hole barrier was optimized to avoid the blocking of photo generated current, maximized the quantum efficiency. The RmaxA product of the PBπBN detector was measured to be 77 Ωcm2 and the dark current density under -0.05V bias was measured to be 8.8×10-4A/cm2 at 80K. The quantum efficiency of gradual hole barrier detector was measured to be 27.2% at 10.6 μm and the quantum efficiency was slowly decreased under reverse bias. The result shows the gradual hole barrier efficiently eliminate the peak barrier in the electron band. The peak detectivity of this graded detector is calculated to be 9.46×1010cm.Hz1/2.W-1 at 10.6 μm.
The barrier enhanced InAs/GaSb long wavelength photodetectors were designed and demonstrated in this paper. A PBIN detector with an electron barrier inserted between P type contactor and absorption region show significantly improved electrical performances compared to a PIN structure. The RmaxA product of the PBIN detector was measured to be 104 Ωcm2 at 80K and 7360 Ωcm2 at 50K. Temperature dependent measurements show that the tunneling currents dominate the dark current below 50K, the generation-recombination (GR) currents dominate from 50K to 90K, and the diffusion current dominate over 90K. The PBIN structure benefits from a lower electric field in the absorption region and therefore, suppressed the tunnel currents and GR currents. To improve the quantum efficiency, Be-doping was employed to convert the conductivity of the long wavelength SL structure, the PN junction moves away from the B-I hetrostructure to the π-N interface, which loses the barrier effect. Therefore, the hole barrier was needed to form a PBπBN structure. In this paper, hole barrier was designed without Al element to form a PBπBN structure. The RmaxA product of the PBπBN detector was measured to be 77 Ωcm2 and the dark current density under -0.05V bias was measured to be 8.8×10-4A/cm2 at 80K. The peak current responsivity at 9.8 μm was 2.15A/W and the quantum efficiency was 26.7%.
InAs/GaSb superlattices are excellent candidates for the third-generation long-wave infrared
and very-long-wave infrared photodetectors due to their special energy structure and theoretical
advantages. To realize their inherent potential, however, superlattice materials with low defect density
and improved device characteristics must be demonstrated. Here we report on the demonstration of highperformance
PBπN photodiodes based on type-II InAs/GaSb superlattices with full cut-off wavelength ~
13.0 μm operating at 77 K. Samples with migration-enhanced epitaxy for interface layers were grown by
molecular beam epitaxy on GaSb substrates and characterized by high-resolution X-ray diffraction and
atomic force microscopy. The FWHM of the 1st-order X-ray diffraction satellite peak of the absorption
layers was only 21.6". The average roughness from AFM on a 2×2 μm2 scan area was less than 0.15 nm.
Optical and electrical measurements of the photodiodes revealed high uniformity of the type-II
superlattice materials. Across the wafer, the detector structure showed a full cut-off wavelength of 13.0
μm at 77 K. The dark current density at -50 mV was 5.1×10-4 A/cm2 and the maximum resistance-area
product (RmaxA) was 128.5 Ω cm2.
KEYWORDS: Interfaces, Gallium antimonide, Laser sintering, Antimony, Camera shutters, Indium arsenide, Superlattices, Atomic force microscopy, Molecular beam epitaxy, Chemical species
In this paper we reported our systematic studies on InSb interface growth in InAs/GaSb SLs structure. Two typical interfaces growth mode, migration-enhanced epitaxy (MEE) and conventional molecular beam epitaxy (MBE), were designed for the 12 ML InAs/12 ML GaSb SLs material and the detail properties were discussion by the experimental measurement and simulation analysis. Our results indicated that the surface of SLs sample with the InSb interface layers grown by MEE method shows smaller RMS both on the 2 μm x 2 μm and 50 μm x 50 μm scan area by AFM measurement, and its PL intensity is about 1.3 times stronger than that of SLs sample grown by MBE. Besides, the MEE samples had significant As composition in InSb interface layers which was extracted by the HRXRD fitting.
Dark current characteristics of long wavelength InAs/GaSb superlattice (SL) detectors have been studied in this paper.
The long wavelength SL structure consists of periodic 14 monolayers (MLs) InAs and 7 MLs GaSb with 50% cutoff
wavelength around 11 μm. Three InAs/GaSb superlattice detectors of PBIN structure were grown at different
temperatures. Wet chemical etching was used to define device mesa. SiO2 was used for device passivation to suppress the sidewall leakage current. Electron barriers were inserted between the absorber region and P-type conducting region to reduce the bulk dark current. The detectors grown at 380oC have the lowest dark current densities as 0.01A/cm2 and the best R0A value as 13 Ωcm2. We simulated four main dark current mechanisms. The result shows that the intrinsic carrier density is extracted to be 3.5E15 cm-3 which matches the C-V measurement very well. And the GR and trap assisted tunnel current dominate the dark current of the device due to the large trap densities and short GR lifetimes.
In the paper we report on a technology of removing the conducting GaSb substrate with the mechanical thinning and wet etch, and then the electrical measurement of non-intentionally doped long-wavelength Infrared (LWIR) type-II InAs/GaSb superlattices (SLs). The SL structures were made of periodic 15 InAs monolayers (MLs) and 7 GaSb MLs with cutoff wavelengths around 11 μm. A etch stop layer was grown between the GaSb substrate and SL for substrate removal for no chemical solution exists with enough selectivity between the GbSb and SLs during the wet etch process. After removing the GaSb substrate, the transport properties measurements of SLs are performed using temperature dependent from 20 k to 296 k and variable magnetic field Hall measurements. It is found that the LWIR SLs is n-type at the all temperatures. Meanwhile, from the result of the mobility spectrum analysis at 76 k, there are more than one type carrier conducting in the LWIR SLs material.
Real-space transfer (RST) has many excellent characteristics, such as high speed, high frequency and negative differential resistance (NDR). RST has drawn a lot of attention since it was proposed by Z.S.Gribnikov in 1972. However, most of the researches about RST were restricted to the classical regime with the hot electron theory. Quantum real-space transfer (QRST) which relies solely on the wave nature of electrons has not been given sufficient attention. In this work, the quantum real-space transfer was deeply investigated. Al0.48In0.52As/GaAs0.51Sb0.49/Al0.48In0.52As alternative symmetry quantum-well structures was designed, and each thickness of the layer is 10 nm, 12 nm, 10nm. We carried out theoretical calculations on the wave-function module and the electrons confinement probability as the function of the in-plane wave-vector. According to our calculations,a sharp electron transfer occurs in the wave-vector range of 3.42×106-7.6×106 /cm. Therefore, it’s feasible to achieve a quantum real-space transfer. We also compared the results to that of the previous quantum structures. At last we propose the optimization to realize quantum real-space transfer (QRST) and discuss the potential applications of the quantum real-space transfer.
High resolution X-ray diffraction is used to study InAs/GaSb superlattices structural properties. The SL materials
were grown by molecular beam epitaxy on the GaSb substrates. We optimize the shutter sequences and soak time to
improve the SL interface and the material quality. The reciprocal space maps show that the materials are almost fully
stained. The angle distance between the zeroth order SL peak and the substrate in ω - 2θ spectrum is about 10 arcsec.
The full-width half-maximum (FWHM) of the zeroth order SL peak is 25 arcsec. Using a four layer model including two
InSb interfaces, we simulated the scanning curve and found there is different layer formed in InAs-on-GaSb and
GaSb-on-InAs interfaces. The arsenic pressure and the interface structure are optimized to get better material quality for
long wavelength SL samples. With optimized growth condition and suitable InSb-like interface structure, high quality SL
samples for both mid and long wavelength range are fabricated. The average roughness from AFM on a 2×2 um2 scan
area is less than 1.5 angstrom.
Optimum quantum well infrared photodetectors (QWIP) structure parameters such as well width and barrier height for a
given peak detection wavelength of 8 μm were designed, based on which GaAs/AlGaAs material with designed structure
was grown and single element QWIP devices were fabricated. In order to accurately calculate the optimum QWIP
structure parameters including well width, barrier height and doping density etc., we took into account higher order
effects such as band nonparabolicity in our calculations. One band effective mass approximation was employed in
modeling and shooting method was used in calculation. We fabricated three kinds of QWIP samples that have 20, 40
and 60 periods of quantum wells respectively. I-V characteristic curves and photoresponse at different temperature were
measured to characterize the detectors. A peak detectivity of 8×1010 cmHz1/2/W was demonstrated by one of our QWIP
devices. Besides, the varying performance of the three samples due to the different repeats of wells is discussed in this
paper.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.