An investigation was made to detect the DNA samples of BALB/c rats, exploiting the technique of b... more An investigation was made to detect the DNA samples of BALB/c rats, exploiting the technique of broadband plasmonic response in the visible spectral regime. In experiments, a non-coherent light beam was physically designed and practically implemented to study the spectral effect due to serial dilution of BALB/c rat’s dried DNA. In particular, three different diluted DNA samples (with ratios of 1:10, 1:20, and 1:40) dried on the surface of a nanolayer gold thin film were considered to retrieve the plasmonic conditions under which the reflectance becomes minimum. The results indicate the most diluted DNA sample exhibits prominent plasmonic conditions, and the resonance wavelengths undergo redshifts with increasing incidence angle (of the p-polarized light). Also, the sensitivity of the configuration is enhanced in the presence of a DNA sample (as compared to the case of non-existence of measurand), which is further increased for larger incidence angles.
We demonstrate a low noise short-wavelength infrared (SWIR) Sb-based type II superlattice (T2SL) ... more We demonstrate a low noise short-wavelength infrared (SWIR) Sb-based type II superlattice (T2SL) avalanche photodiodes (APD). The SWIR GaSb/(AlAsSb/GaSb) APD structure was designed based on impact ionization engineering and grown by molecular beam epitaxy on GaSb substrate. At room temperature, the device exhibits a 50 % cutoff wavelength of 1.74 µm. The device revealed to have electron dominated avalanching mechanism with a gain value of 48 at room temperature. The electron and hole impact ionization coefficients were calculated and compared to give better prospect of the performance of the device. Low excess noise, as characterized by the carrier ionization ratio of ~ 0.07, has been achieved.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Third generation of infrared imagers demand performances for higher detectivity, higher operating... more Third generation of infrared imagers demand performances for higher detectivity, higher operating temperature, higher resolution, and multi-color detection all accomplished with better yield and lower manufacturing costs. Antimonide-based gap-engineered Type-II superlattices (T2SLs) material system is considered as a potential alternative for Mercury- Cadmium-Telluride (HgCdTe) technology in all different infrared detection regimes from short to very long wavelengths for the third generation of infrared imagers. 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. We will present the most recent research results on Antimonide-based gap-engineered Type-II superlattices, such as high-performance dual-band SWIR/MWIR photo-detectors and focal plane arrays for different infrared regimes, toward the third generation of infrared imaging systems at the Center for Quantum Devices. Comparing metal-organic chemical vapor deposition (MOCVD), vs molecular beam epitaxy (MBE).
Abstract Type-II InAs/GaSb superlattices (T2SLs) has drawn a lot of attention since it was introd... more Abstract Type-II InAs/GaSb superlattices (T2SLs) has drawn a lot of attention since it was introduced in 1970, especially for infrared detection as a system of multi-interacting quantum wells. In recent years, T2SL material system has experienced incredible improvements in material quality, device structure designs and device fabrication process, which elevated the performances of T2SL-based photo-detectors to a comparable level to the state-of-the-art material systems for infrared detection such as Mercury Cadmium Telluride (MCT). As a pioneer in the field, center for quantum devices (CQD) has been involved in growth, design, characterization, and introduction of T2SL material system for infrared photodetection. In this review paper, we will present the latest development of bias-selectable multi-band infrared photodetectors at the CQD, based on InAs/GaSb/AlSb and InAs/InAs1-xSbx type-II superlattice.
We fabricated β-Gaalt;subagt;2alt;/subagt;Oalt;subagt;3alt;/subagt;:Si metal-oxide field-effect t... more We fabricated β-Gaalt;subagt;2alt;/subagt;Oalt;subagt;3alt;/subagt;:Si metal-oxide field-effect transistors (MOSFETs) on c-plane sapphire substrate which typically showed maximum drain current of 100 mA/mm. β-Gaalt;subagt;2alt;/subagt;Oalt;subagt;3alt;/subagt;:Si thin films were realized on c-plane sapphire substrate through a combination of metalorganic chemical vapor deposition (MOCVD) and post-annealing. The MOSFET device presented excellent on/off drain current ratio of ~10alt;supagt;11alt;/supagt; with very low gate leakage current, sharp pinch off behavior, and a breakdown voltage of 400 V at VG =-40 V. The growth and fabrication of β-Gaalt;subagt;2alt;/subagt;Oalt;subagt;3alt;/subagt;:Si MOSFETs on c-plane sapphire is valuable its demonstration of the great potential for future high-power electronic devices.
We report design, growth, and characterization of midwavelength infrared nBn photodetectors based... more We report design, growth, and characterization of midwavelength infrared nBn photodetectors based on a type-II InAs/InAs1-xSbx superlattice on a GaSb substrate grown by metal-organic chemical vapor deposition. An InAs/AlAs1-ySby/InAs/InAs1-xSbx superlattice design was used as the large bandgap electron barrier in the photodetectors. At 150 K, the photodetector exhibits a peak responsivity of 1.23 A/W, corresponding to a quantum efficiency of 41% at an applied bias voltage of −100 mV under front-side illumination, with a 50% cut-off wavelength of 4.6 μm. With an R × A of 356 Ω cm2 and a dark current density of 1.6 × 10−4 A/cm2 under an applied bias of −100 mV at 150 K, the photodetector exhibits a specific detectivity of 1.4 × 1011 cm Hz1/2/W.
A two terminal extended short wavelength infrared heterojunction phototransistor based on type-II... more A two terminal extended short wavelength infrared heterojunction phototransistor based on type-II InAs/AlSb/GaSb on a GaSb substrate is designed, fabricated, and investigated. With the base thickness of 40 nm, the device exhibited a 100% cut-off wavelength of ∼2.3 μm at 300 K. The saturated peak responsivity value is 320.5 A/W at 300 K, under front-side illumination without any antireflection coating. A saturated optical gain of 245 at 300 K was measured. At the same temperature, the device exhibited a collector dark current density (at unity optical gain) and a DC current gain of 7.8 × 10−3 A/cm2 and 1100, respectively. The device exhibited a saturated dark current shot noise limited specific detectivity of 4.9 × 1011 cm·Hz1/2/W at 300 K which remains constant over a broad range of wavelengths and applied biases.
Different passivation techniques are investigated for reducing leakage current in small pixel (do... more Different passivation techniques are investigated for reducing leakage current in small pixel (down to 9 μm) heterostructure photodetectors designed for the short-wavelength infrared range. Process evaluation test chips were fabricated using the same process as for focal plane arrays. Arrays of small photodetectors were electrically characterized under dark conditions from 150 K to room temperature. In order to evaluate the leakage current, we studied the relation between the inverse of dynamic resistance at −20 mV and zero bias and perimeter over area P/A ratio as the pixel size is scaled down. At 150 K, leakage current arising from the perimeter dominates while bulk leakage dominates at room temperature. We find that in shortwave devices directly underfilling hybridized devices with a thermoset epoxy resin without first doing any additional passivation/protection after etching gives the lowest leakage with a surface resistance of 4.2 × 109 and 8.9 × 103 Ω cm−1 at 150 and 300 K, for −20 mV of bias voltage, respectively.
We report the growth and characterization of long wavelength infrared type-II InAs/InAs1-xSbx sup... more We report the growth and characterization of long wavelength infrared type-II InAs/InAs1-xSbx superlattice photodiodes with a 50% cut-off wavelength at 8.0 μm on a GaSb substrate grown by metalorganic chemical vapor deposition. At 77 K, the photodiodes exhibited a differential resistance at zero bias (R0A) of 8.0 Ω cm2 and a peak responsivity of 1.26 A/W corresponding to a quantum efficiency of 21%. A specific detectivity of 5.4 × 1010 cm Hz1/2/W was achieved at 7.5 μm.
We present an intial demonstration of a 1280 × 1024 extended short-wavelength infrared focal plan... more We present an intial demonstration of a 1280 × 1024 extended short-wavelength infrared focal plane array (FPA) imager with 12 μm pixel-pitch based on type–II InAs/AlSb/GaSb superlattice heterojunction photodetectors, with a novel bandstructure-engineered photo-generated carrier extractor as the window layer in the hetero structure to efficiently extract the photo-generated carriers. This heterostructure with a larger bandgap top window/contact layer leads to the device having lower dark current density compared to conventional pn junction devices. The large format FPA was fabricated with 12 μm pixel-pitch using a developed fabrication process. Test pixels fabricated separately exhibit 100% cut–off wavelengths of ~2.22, ~2.34 μm, and ~2.45 μm at 150, 200 K, and 300 K. The test devices achieve saturated quantum efficiency values under zero bias of 54.3% and 68.4% at 150 and 300 K, under back-side illumination and without any anti-reflection coating. At 150 K, these photodetectors exhibit dark current density of 1.63 × 10−7 A cm−2 under −20 mV applied bias providing a specific detectivity of 1.01 × 1011 cm Hz1/2/W at 1.9 μm.
An extended short-wavelength nBn InAs/GaSb/AlSb type-II superlattice-based infrared focal plane a... more An extended short-wavelength nBn InAs/GaSb/AlSb type-II superlattice-based infrared focal plane array imager was demonstrated. A newly developed InAsSb/GaSb superlattice design was used as the large-bandgap electron barrier in this photodetector. The large band gap electron-barrier design in this nBn photodetector architecture leads to the device having lower dark current densities. A new bi-layer etch-stop scheme using a combination of InAsSb bulk and AlAsSb/GaSb superlattice layers was introduced to allow complete substrate removal and a shorter wavelength cut-on. Test pixels exhibit 100% cutoff wavelengths of ∼2.30 and ∼2.48 μm at 150 and 300 K, respectively. The devices achieve saturated quantum efficiency values of 59.7% and 63.8% at 150 and 300 K, respectively, under backside illumination and without any antireflection coating. At 150 K, photodetectors exhibit dark current density of 8.75×10 A/cm under -400 mV applied bias, providing specific detectivity of 2.82×10 cm·Hz/W...
A versatile infrared imager capable of imaging the near-visible to the extended short-wavelength ... more A versatile infrared imager capable of imaging the near-visible to the extended short-wavelength infrared (e-SWIR) is demonstrated using e-SWIR InAs/GaSb/AlSb type-II superlattice-based photodiodes. A bi-layer etch-stop scheme consisting of bulk InAs0.91Sb0.09 and AlAs0.1Sb0.9/GaSb superlattice layers is introduced for substrate removal from the hybridized back-side illuminated photodetectors. The implementation of this new technique on an e-SWIR focal plane array results in a significant enhancement in the external quantum efficiency (QE) in the 1.8-0.8 μm spectral region, while maintaining a high QE at wavelengths longer than 1.8 μm. Test pixels exhibit 100% cutoff wavelengths of ∼2.1 and ∼2.25 μm at 150 and 300 K, respectively. They achieve saturated QE values of 56% and 68% at 150 and 300 K, respectively, under back-side illumination and without any anti-reflection coating. At 150 K, the photodetectors (27 μm×27 μm area) exhibit a dark current density of 4.7×10-7 A/cm2 under...
Extended short-wavelength infrared nBn photodetectors based on type-II InAs/AlSb/GaSb superlattic... more Extended short-wavelength infrared nBn photodetectors based on type-II InAs/AlSb/GaSb superlattices on GaSb substrate have been demonstrated. An AlAs0.10Sb0.90/GaSb H-structure superlattice design was used as the large-bandgap electron-barrier in these photodetectors. The photodetector is designed to have a 100% cut-off wavelength of ∼2.8 μm at 300 K. The photodetector exhibited a room-temperature (300 K) peak responsivity of 0.65 A/W at 1.9 μm, corresponding to a quantum efficiency of 41% at zero bias under front-side illumination, without any anti-reflection coating. With an R × A of 78 Ω·cm2 and a dark current density of 8 × 10−3 A/cm2 under −400 mV applied bias at 300 K, the nBn photodetector exhibited a specific detectivity of 1.51 × 1010 cm·Hz1/2/W. At 150 K, the photodetector exhibited a dark current density of 9.5 × 10−9 A/cm2 and a quantum efficiency of 50%, resulting in a detectivity of 1.12 × 1013 cm·Hz1/2/W.
A mid-wavelength infrared heterojunction phototransistor based on type-II InAs/AlSb/GaSb superlat... more A mid-wavelength infrared heterojunction phototransistor based on type-II InAs/AlSb/GaSb superlattices on GaSb substrate has been demonstrated. Near a wavelength of 4 μm saturated optical gains of 668 and 639 at 77 and 150 K, respectively, are demonstrated over a wide dynamic range. At 150 K, the unity optical gain collector dark current density and DC current gain are 1 × 10−3 A/cm2 and 3710, respectively. This demonstrates the potential for use in high-speed applications. In addition, the phototransistor exhibits a specific detectivity value that is four times higher compared with a state-of-the-art type-II superlattice-based photodiode with a similar cut-off wavelength at 150 K.
An investigation was made to detect the DNA samples of BALB/c rats, exploiting the technique of b... more An investigation was made to detect the DNA samples of BALB/c rats, exploiting the technique of broadband plasmonic response in the visible spectral regime. In experiments, a non-coherent light beam was physically designed and practically implemented to study the spectral effect due to serial dilution of BALB/c rat’s dried DNA. In particular, three different diluted DNA samples (with ratios of 1:10, 1:20, and 1:40) dried on the surface of a nanolayer gold thin film were considered to retrieve the plasmonic conditions under which the reflectance becomes minimum. The results indicate the most diluted DNA sample exhibits prominent plasmonic conditions, and the resonance wavelengths undergo redshifts with increasing incidence angle (of the p-polarized light). Also, the sensitivity of the configuration is enhanced in the presence of a DNA sample (as compared to the case of non-existence of measurand), which is further increased for larger incidence angles.
We demonstrate a low noise short-wavelength infrared (SWIR) Sb-based type II superlattice (T2SL) ... more We demonstrate a low noise short-wavelength infrared (SWIR) Sb-based type II superlattice (T2SL) avalanche photodiodes (APD). The SWIR GaSb/(AlAsSb/GaSb) APD structure was designed based on impact ionization engineering and grown by molecular beam epitaxy on GaSb substrate. At room temperature, the device exhibits a 50 % cutoff wavelength of 1.74 µm. The device revealed to have electron dominated avalanching mechanism with a gain value of 48 at room temperature. The electron and hole impact ionization coefficients were calculated and compared to give better prospect of the performance of the device. Low excess noise, as characterized by the carrier ionization ratio of ~ 0.07, has been achieved.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Third generation of infrared imagers demand performances for higher detectivity, higher operating... more Third generation of infrared imagers demand performances for higher detectivity, higher operating temperature, higher resolution, and multi-color detection all accomplished with better yield and lower manufacturing costs. Antimonide-based gap-engineered Type-II superlattices (T2SLs) material system is considered as a potential alternative for Mercury- Cadmium-Telluride (HgCdTe) technology in all different infrared detection regimes from short to very long wavelengths for the third generation of infrared imagers. 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. We will present the most recent research results on Antimonide-based gap-engineered Type-II superlattices, such as high-performance dual-band SWIR/MWIR photo-detectors and focal plane arrays for different infrared regimes, toward the third generation of infrared imaging systems at the Center for Quantum Devices. Comparing metal-organic chemical vapor deposition (MOCVD), vs molecular beam epitaxy (MBE).
Abstract Type-II InAs/GaSb superlattices (T2SLs) has drawn a lot of attention since it was introd... more Abstract Type-II InAs/GaSb superlattices (T2SLs) has drawn a lot of attention since it was introduced in 1970, especially for infrared detection as a system of multi-interacting quantum wells. In recent years, T2SL material system has experienced incredible improvements in material quality, device structure designs and device fabrication process, which elevated the performances of T2SL-based photo-detectors to a comparable level to the state-of-the-art material systems for infrared detection such as Mercury Cadmium Telluride (MCT). As a pioneer in the field, center for quantum devices (CQD) has been involved in growth, design, characterization, and introduction of T2SL material system for infrared photodetection. In this review paper, we will present the latest development of bias-selectable multi-band infrared photodetectors at the CQD, based on InAs/GaSb/AlSb and InAs/InAs1-xSbx type-II superlattice.
We fabricated β-Gaalt;subagt;2alt;/subagt;Oalt;subagt;3alt;/subagt;:Si metal-oxide field-effect t... more We fabricated β-Gaalt;subagt;2alt;/subagt;Oalt;subagt;3alt;/subagt;:Si metal-oxide field-effect transistors (MOSFETs) on c-plane sapphire substrate which typically showed maximum drain current of 100 mA/mm. β-Gaalt;subagt;2alt;/subagt;Oalt;subagt;3alt;/subagt;:Si thin films were realized on c-plane sapphire substrate through a combination of metalorganic chemical vapor deposition (MOCVD) and post-annealing. The MOSFET device presented excellent on/off drain current ratio of ~10alt;supagt;11alt;/supagt; with very low gate leakage current, sharp pinch off behavior, and a breakdown voltage of 400 V at VG =-40 V. The growth and fabrication of β-Gaalt;subagt;2alt;/subagt;Oalt;subagt;3alt;/subagt;:Si MOSFETs on c-plane sapphire is valuable its demonstration of the great potential for future high-power electronic devices.
We report design, growth, and characterization of midwavelength infrared nBn photodetectors based... more We report design, growth, and characterization of midwavelength infrared nBn photodetectors based on a type-II InAs/InAs1-xSbx superlattice on a GaSb substrate grown by metal-organic chemical vapor deposition. An InAs/AlAs1-ySby/InAs/InAs1-xSbx superlattice design was used as the large bandgap electron barrier in the photodetectors. At 150 K, the photodetector exhibits a peak responsivity of 1.23 A/W, corresponding to a quantum efficiency of 41% at an applied bias voltage of −100 mV under front-side illumination, with a 50% cut-off wavelength of 4.6 μm. With an R × A of 356 Ω cm2 and a dark current density of 1.6 × 10−4 A/cm2 under an applied bias of −100 mV at 150 K, the photodetector exhibits a specific detectivity of 1.4 × 1011 cm Hz1/2/W.
A two terminal extended short wavelength infrared heterojunction phototransistor based on type-II... more A two terminal extended short wavelength infrared heterojunction phototransistor based on type-II InAs/AlSb/GaSb on a GaSb substrate is designed, fabricated, and investigated. With the base thickness of 40 nm, the device exhibited a 100% cut-off wavelength of ∼2.3 μm at 300 K. The saturated peak responsivity value is 320.5 A/W at 300 K, under front-side illumination without any antireflection coating. A saturated optical gain of 245 at 300 K was measured. At the same temperature, the device exhibited a collector dark current density (at unity optical gain) and a DC current gain of 7.8 × 10−3 A/cm2 and 1100, respectively. The device exhibited a saturated dark current shot noise limited specific detectivity of 4.9 × 1011 cm·Hz1/2/W at 300 K which remains constant over a broad range of wavelengths and applied biases.
Different passivation techniques are investigated for reducing leakage current in small pixel (do... more Different passivation techniques are investigated for reducing leakage current in small pixel (down to 9 μm) heterostructure photodetectors designed for the short-wavelength infrared range. Process evaluation test chips were fabricated using the same process as for focal plane arrays. Arrays of small photodetectors were electrically characterized under dark conditions from 150 K to room temperature. In order to evaluate the leakage current, we studied the relation between the inverse of dynamic resistance at −20 mV and zero bias and perimeter over area P/A ratio as the pixel size is scaled down. At 150 K, leakage current arising from the perimeter dominates while bulk leakage dominates at room temperature. We find that in shortwave devices directly underfilling hybridized devices with a thermoset epoxy resin without first doing any additional passivation/protection after etching gives the lowest leakage with a surface resistance of 4.2 × 109 and 8.9 × 103 Ω cm−1 at 150 and 300 K, for −20 mV of bias voltage, respectively.
We report the growth and characterization of long wavelength infrared type-II InAs/InAs1-xSbx sup... more We report the growth and characterization of long wavelength infrared type-II InAs/InAs1-xSbx superlattice photodiodes with a 50% cut-off wavelength at 8.0 μm on a GaSb substrate grown by metalorganic chemical vapor deposition. At 77 K, the photodiodes exhibited a differential resistance at zero bias (R0A) of 8.0 Ω cm2 and a peak responsivity of 1.26 A/W corresponding to a quantum efficiency of 21%. A specific detectivity of 5.4 × 1010 cm Hz1/2/W was achieved at 7.5 μm.
We present an intial demonstration of a 1280 × 1024 extended short-wavelength infrared focal plan... more We present an intial demonstration of a 1280 × 1024 extended short-wavelength infrared focal plane array (FPA) imager with 12 μm pixel-pitch based on type–II InAs/AlSb/GaSb superlattice heterojunction photodetectors, with a novel bandstructure-engineered photo-generated carrier extractor as the window layer in the hetero structure to efficiently extract the photo-generated carriers. This heterostructure with a larger bandgap top window/contact layer leads to the device having lower dark current density compared to conventional pn junction devices. The large format FPA was fabricated with 12 μm pixel-pitch using a developed fabrication process. Test pixels fabricated separately exhibit 100% cut–off wavelengths of ~2.22, ~2.34 μm, and ~2.45 μm at 150, 200 K, and 300 K. The test devices achieve saturated quantum efficiency values under zero bias of 54.3% and 68.4% at 150 and 300 K, under back-side illumination and without any anti-reflection coating. At 150 K, these photodetectors exhibit dark current density of 1.63 × 10−7 A cm−2 under −20 mV applied bias providing a specific detectivity of 1.01 × 1011 cm Hz1/2/W at 1.9 μm.
An extended short-wavelength nBn InAs/GaSb/AlSb type-II superlattice-based infrared focal plane a... more An extended short-wavelength nBn InAs/GaSb/AlSb type-II superlattice-based infrared focal plane array imager was demonstrated. A newly developed InAsSb/GaSb superlattice design was used as the large-bandgap electron barrier in this photodetector. The large band gap electron-barrier design in this nBn photodetector architecture leads to the device having lower dark current densities. A new bi-layer etch-stop scheme using a combination of InAsSb bulk and AlAsSb/GaSb superlattice layers was introduced to allow complete substrate removal and a shorter wavelength cut-on. Test pixels exhibit 100% cutoff wavelengths of ∼2.30 and ∼2.48 μm at 150 and 300 K, respectively. The devices achieve saturated quantum efficiency values of 59.7% and 63.8% at 150 and 300 K, respectively, under backside illumination and without any antireflection coating. At 150 K, photodetectors exhibit dark current density of 8.75×10 A/cm under -400 mV applied bias, providing specific detectivity of 2.82×10 cm·Hz/W...
A versatile infrared imager capable of imaging the near-visible to the extended short-wavelength ... more A versatile infrared imager capable of imaging the near-visible to the extended short-wavelength infrared (e-SWIR) is demonstrated using e-SWIR InAs/GaSb/AlSb type-II superlattice-based photodiodes. A bi-layer etch-stop scheme consisting of bulk InAs0.91Sb0.09 and AlAs0.1Sb0.9/GaSb superlattice layers is introduced for substrate removal from the hybridized back-side illuminated photodetectors. The implementation of this new technique on an e-SWIR focal plane array results in a significant enhancement in the external quantum efficiency (QE) in the 1.8-0.8 μm spectral region, while maintaining a high QE at wavelengths longer than 1.8 μm. Test pixels exhibit 100% cutoff wavelengths of ∼2.1 and ∼2.25 μm at 150 and 300 K, respectively. They achieve saturated QE values of 56% and 68% at 150 and 300 K, respectively, under back-side illumination and without any anti-reflection coating. At 150 K, the photodetectors (27 μm×27 μm area) exhibit a dark current density of 4.7×10-7 A/cm2 under...
Extended short-wavelength infrared nBn photodetectors based on type-II InAs/AlSb/GaSb superlattic... more Extended short-wavelength infrared nBn photodetectors based on type-II InAs/AlSb/GaSb superlattices on GaSb substrate have been demonstrated. An AlAs0.10Sb0.90/GaSb H-structure superlattice design was used as the large-bandgap electron-barrier in these photodetectors. The photodetector is designed to have a 100% cut-off wavelength of ∼2.8 μm at 300 K. The photodetector exhibited a room-temperature (300 K) peak responsivity of 0.65 A/W at 1.9 μm, corresponding to a quantum efficiency of 41% at zero bias under front-side illumination, without any anti-reflection coating. With an R × A of 78 Ω·cm2 and a dark current density of 8 × 10−3 A/cm2 under −400 mV applied bias at 300 K, the nBn photodetector exhibited a specific detectivity of 1.51 × 1010 cm·Hz1/2/W. At 150 K, the photodetector exhibited a dark current density of 9.5 × 10−9 A/cm2 and a quantum efficiency of 50%, resulting in a detectivity of 1.12 × 1013 cm·Hz1/2/W.
A mid-wavelength infrared heterojunction phototransistor based on type-II InAs/AlSb/GaSb superlat... more A mid-wavelength infrared heterojunction phototransistor based on type-II InAs/AlSb/GaSb superlattices on GaSb substrate has been demonstrated. Near a wavelength of 4 μm saturated optical gains of 668 and 639 at 77 and 150 K, respectively, are demonstrated over a wide dynamic range. At 150 K, the unity optical gain collector dark current density and DC current gain are 1 × 10−3 A/cm2 and 3710, respectively. This demonstrates the potential for use in high-speed applications. In addition, the phototransistor exhibits a specific detectivity value that is four times higher compared with a state-of-the-art type-II superlattice-based photodiode with a similar cut-off wavelength at 150 K.
Type-II InAs/GaSb superlattices (T2SLs) has drawn a lot of attention since it was introduced in 1... more Type-II InAs/GaSb superlattices (T2SLs) has drawn a lot of attention since it was introduced in 1970, especially for infrared detection as a system of multi-interacting quantum wells. In recent years, T2SL material system has experienced incredible improvements in material quality, device structure designs and device fabrication process, which elevated the performances of T2SL-based photo-detectors to a comparable level to the state-of-the-art material systems for infrared detection such as Mercury Cadmium Telluride (MCT). As a pioneer in the field, center for quantum devices (CQD) has been involved in growth, design, characterization, and introduction of T2SL material system for infrared photodetection. In this review paper, we will present the latest development of bias-selectable multi-band infrared photodetectors at the CQD, based on InAs/GaSb/AlSb and InAs/InAs1-xSbx type-II superlattice.
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