Engineering topics
Ting, David Z.-Y.
Publications and source records attributed to Ting, David Z.-Y..
Performance and Radiation Tolerance of InAs/GaSb LWIR Detectors Based on CBIRD Design
We report our recent developments of antimonide based infrared photodetectors utilizing a complementary barrier infrared detector (CBIRD) design. The new generation of devices can operate close to zero bias with the same quantum efficiency as the initial design. 320x256 pixel long-wavelength infrared focal plane arrays utilizing optimized design have been demonstrated with 8.8 µm cutoff wavelength and noise equivalent differential temperature of 26 mK at operating temperature of 80 K for 300 K background and f/2 optics. As CBIRD detectors became valuable candidates for space-based instruments, question of their radiation tolerance became important. Here, we report our investigations of the proton irradiation effects on the photodetector performance.
Performance and Radiation Tolerance of InAs/GaSb LWIR Detectors Based on CBIRD Design
No abstract available
Radiation Tolerance Studies of Long Wavelength Infrared InAs/GaSb Detectors
In this work we investigated the effect of proton irradiation on the performance of long wavelength infrared (LWIR) InAs/GaSb photodiodes (λ(sub c) = 10.2µm) based on the complementary barrier infrared detector (CBIRD) design. We found that irradiation with 68MeV protons up to the total ionizing dose TID = 200 kRad results in only small (about 15%) decrease of the Quantum Efficiency and does not increase the operational bias of the photodiodes. However, the irradiation causes a significant increase of the dark current from j(sub d) = 5x10(exp -5) A/sq cm at V(sub b) = 0.1V and T = 80K to j(sub d) = 6x10(exp -3) A/sq cm at TID = 200 kRad. This change in the dark current mechanism can be attributed to the onset of surface leakage current, generated by the trap assisted tunneling processes in the proton displacement damage areas near the device sidewalls.
Radiation Tolerance Studies of Long Wavelength Infrared InAs/GaSb Detectors
Introduction: Barrier Infrared Detector (BIRD), Complementary Barrier Infrared Detector (CBIRD); Proton radiation effect on CBIRD performance: Dark current, Spectral characteristics; Summary.
Multi-color QWIP FPAs for hyperspectral thermal emission instruments
Infrared focal plane arrays (FPAs) covering broad mid- and long-IR spectral ranges are the central parts of the spectroscopic and imaging instruments in several Earth and planetary science missions. To be implemented in the space instrument these FPAs need to be large-format, uniform, reproducible, low-cost, low 1/f noise, and radiation hard. Quantum Well Infrared Photodetectors (QWIPs), which possess all needed characteristics, have a great potential for implementation in the space instruments. However a standard QWIP has only a relatively narrow spectral coverage. A multi-color QWIP, which is compromised of two or more detector stacks, can to be used to cover the broad spectral range of interest. We will discuss our recent work on development of multi-color QWIP for Hyperspectral Thermal Emission Spectrometer instruments. We developed QWIP compromising of two stacks centered at 9 and 10.5 μm, and featuring 9 grating regions optimized to maximize the responsivity in the individual subbands across the 7.5-12 μm spectral range. The demonstrated 1024x1024 QWIP FPA exhibited excellent performance with operability exceeding 99% and noise equivalent differential temperature of less than 15 mK across the entire 7.5-12 μm spectral range.
Multi-Color QWIP FPAs for Hyperspectral Thermal Emission Instruments
Infrared focal plane arrays (FPAs) covering broad mid- and long-IR spectral ranges are the central parts of the spectroscopic and imaging instruments in several Earth and planetary science missions. To be implemented in the space instrument these FPAs need to be large-format, uniform, reproducible, low-cost, low 1/f noise, and radiation hard. Quantum Well Infrared Photodetectors (QWIPs), which possess all needed characteristics, have a great potential for implementation in the space instruments. However a standard QWIP has only a relatively narrow spectral coverage. A multi-color QWIP, which is compromised of two or more detector stacks, can to be used to cover the broad spectral range of interest. We will discuss our recent work on development of multi-color QWIP for Hyperspectral Thermal Emission Spectrometer instruments. We developed QWIP compromising of two stacks centered at 9 and 10.5 ?m, and featuring 9 grating regions optimized to maximize the responsivity in the individual subbands across the 7.5-12 ?m spectral range. The demonstrated 1024x1024 QWIP FPA exhibited excellent performance with operability exceeding 99% and noise equivalent differential temperature of less than 15 mK across the entire 7.5-12 ?m spectral range.
High-Performance LWIR Superlattice Detectors and FPA Based on CBIRD Design
We report our recent efforts on advancing of antimonide superlattice based infrared photodetectors and demonstration of Focal Plane Arrays (FPA) based on a complementary barrier infrared detector (CBIRD) design. By optimizing design and growth condition we succeeded to reduce the operational bias of CBIRD single pixel detector without increase of dark current or degradation of quantum efficiency. We demonstrated a 1024x1024 pixel long-wavelength infrared focal plane array utilizing CBIRD design. An 11.5 ?m cutoff FPA without anti-reflection coating has yielded noise equivalent differential temperature of 53 mK at operating temperature of 80 K, with 300 K background and cold-stop. In addition, we demonstrated 320x256 format FPA based on the n-CBIRD design. The resulting FPAs yielded noise equivalent differential temperature of 26 mK at operating temperature of 80 K, with 300 K background and cold-stop. These results advance state-of-the art of superlattice detectors and demonstrated advantages of CBIRD architecture for realization of FPA.
320 x 256 Complementary Barrier Infrared Detector Focal Plane Array for Long-Wave Infrared Imaging
A 320 x 256 Complementary Barrier Infrared (CBIRD) focal plane array for long-wavelength infrared (LWIR) imaging is reported. The arrays were grown by molecular beam expitaxy (MBE) with a 300 period 1.9 um thick absorber. The mean dark current density of 2.2 x 10-4 A/cm2 was measured at an operating bias of 128 mV with a long wavelength cutoff of 8.8 ?m observed at 50% of the peak. The maximum quantum efficiency was 54% measured at 5.6 ?m. Operating at T = 80K, the array yielded an 81% fill factor with 97% operability. Good imagery with a mean noise equivalent different temperature (NE?T) of 18.6 mK and a mean detectivity of D* = 1.3 x 1011 cm-Hz1/2/W was achieved. The substrate was thinned using mechanical lapping and neither an AR coating nor a passivation layer was applied. This article provides the details of the fabrication process for achieving low-dark current LWIR CBIRD arrays. Discussion for an effective hard mask for excellent pattern transfer is given and appropriate mounting techniques for good thermal contact during the dry etching process is described. The challenges and differences between etching large 200 ?m test diodes and small 28 ?m FPA pixels are given.
High-Performance LWIR Superlattice Detectors and FPA Based on CBIRD Design
We report our recent efforts on advancing of antimonide superlattice based infrared photodetectors and demonstration of focal plane arrays based on a complementary barrier infrared detector (CBIRD) design. By optimizing design and growth condition we succeeded to reduce the operational bias of CBIRD single pixel detector without increase of dark current or degradation of quantum efficiency. We demonstrated a 1024x1024 pixel long-wavelength infrared focal plane array utilizing CBIRD design. An 11.5 micrometer cutoff focal plane without anti-reflection coating has yielded noise equivalent differential temperature of 53 mK at operating temperature of 80 K, with 300 K background and cold-stop. Imaging results from a recent 10 micrometer cutoff focal plane array are also presented. These results advance state-of-the art of superlattice detectors and demonstrated advantages of CBIRD architecture for realization of FPA.
High-Performance LWIR Superlattice Detectors and FPA Based on CBIRD Design
We report our recent efforts on advancing of antimonide superlattice based infrared photodetectors and demonstration of focal plane arrays based on a complementary barrier infrared detector (CBIRD) design. By optimizing design and growth condition we succeeded to reduce the operational bias of CBIRD single pixel detector without increase of dark current or degradation of quantum efficiency. We demonstrated a 1024x1024 pixel long-waveleng thinfrared focal plane array utilizing CBIRD design. An 11.5 micrometer cutoff focal plane without anti-reflection coating has yielded noise equivalent differential temperature of 53 mK at operating temperature of 80 K, with 300 K background and cold-stop. Imaging results from a recent 10 micrometer cutoff focal plane array are also presented. These results advance state-of-the art of superlattice detectors and demonstrated advantages of CBIRD architecture for realization of FPA.
Electron-Spin Filters Based on the Rashba Effect
Semiconductor electron-spin filters of a proposed type would be based on the Rashba effect, which is described briefly below. Electron-spin filters more precisely, sources of spin-polarized electron currents have been sought for research on, and development of, the emerging technological discipline of spintronics (spin-based electronics). There have been a number of successful demonstrations of injection of spin-polarized electrons from diluted magnetic semiconductors and from ferromagnetic metals into nonmagnetic semiconductors. In contrast, a device according to the proposal would be made from nonmagnetic semiconductor materials and would function without an applied magnetic field. The Rashba effect, named after one of its discoverers, is an energy splitting, of what would otherwise be degenerate quantum states, caused by a spin-orbit interaction in conjunction with a structural-inversion asymmetry in the presence of interfacial electric fields in a semiconductor heterostructure. The magnitude of the energy split is proportional to the electron wave number. The present proposal evolved from recent theoretical studies that suggested the possibility of devices in which electron energy states would be split by the Rashba effect and spin-polarized currents would be extracted by resonant quantum-mechanical tunneling. Accordingly, a device according to the proposal would be denoted an asymmetric resonant interband tunneling diode [a-RITD]. An a-RITD could be implemented in a variety of forms, the form favored in the proposal being a double-barrier heterostructure containing an asymmetric quantum well. It is envisioned that a-RITDs would be designed and fabricated in the InAs/GaSb/AlSb material system for several reasons: Heterostructures in this material system are strong candidates for pronounced Rashba spin splitting because InAs and GaSb exhibit large spin-orbit interactions and because both InAs and GaSb would be available for the construction of highly asymmetric quantum wells. This mate-rial system affords a variety of energy-band alignments that can be exploited to obtain resonant tunneling and other desired effects. The no-common-atom InAs/GaSb and InAs/AlSb interfaces would present opportunities for engineering interface potentials for optimizing Rashba spin splitting.