Type-II Antimonide-based Superlattices for High Performance Infrared Detectors and Imagers

Antimonide-based type-II superlattices have demonstrated unique properties that are extremely desirable for making high-performance infrared photodetectors and focal plane arrays (FPAs). However, this technology still needs to be further developed to be able to substitute existing technologies, mainly Mercury-Cadmium-Telluride compounds (HgCdTe). In mid-wavelength infrared (MWIR), high operating temperature is the ultimate goal which needs more investigation in order to find a reliable passivation technique, further improvement of the electrical performance, and the reduction of cost.;The focus of this work is, partially, to demonstrate that Type-II InAs/GaSb superlattices can perform high-quality infrared imaging in mid-wavelength infrared regime. Theoretically, photodetectors and focal plane arrays (FPAs) based on this technology could be operated at higher temperatures, with lower dark currents than the leading HgCdTe platform. However, such performances have not been demonstrated yet. This effort will focus on the design, growth, and measurement of MWIR photodetectors and FPAs with performance similar to existing infrared cameras.;To raise the operating temperature of MWIR photodetectors, the tunneling barrier was re-designed along with reducing the concentration of minority carriers in the active region by increasing the doping level and optimizing the doping technique and proper use of a capping layer resulted in 5°C increase in maximum temperature for background limited performance to 195 K.;FPAs were also fabricated, using the new photodetector design, to demonstrate a camera that presented similar performance to HgCdTe and that could be operated up to room temperature. At 81K, the camera could detect temperature differences as low as 10 mK for an integration time shorter than 8 ms using F/2.3 optics. It demonstrated an operability of 99.5% at this operating temperature.;The second part of this work, we addressed the problem of low QE in LWIR InAs/InAs1-xSbx type-II superlattice-based photodetectors which are expected to have superior performance compare to the conventional InAs/GaSb type-II superlattice-based photodetectors. We proposed new superlattice design to overcome this problem which resulted in the design, growth, and characterization of a high-performance LWIR nBn photodetector based on InAs/InAs 1-xSbx T2SLs on GaSb substrate. The device exhibited a 50% cut-off wavelength of 10 um at 77 K. At the peak responsivity, the photodetector exhibited QE and responsivity of 54% and 3.47 A/W, respectively, under front-side illumination and without any AR coating. At -90 mV, the device exhibited dark current density and RxA of 4.4x10-4 A/cm 2 and 119 Ohm•cm2, respectively, at 77 K. At 7.9 microm, the device exhibited a saturated dark current shot noise limited specific detectivity of 2.8x1011 cm•√ Hz/W at 77 K which stays constant over a broad range of wavelengths and applied bias voltages.;The third generation of infrared cameras is based on multi-band imaging concept in order to improve the recognition capabilities of the imager. Therefore, we dedicated the third part of this work to demonstration of the design, growth, and characterization of a high-performance bias-selectable dual-band MWIR-LWIR photodetectors based on InAs/InAs1-xSbx T2SLs. The MWIR channel achieved a saturated quantum efficiency of 45% at peak responsivity under front-side illumination and without any AR coating. At 100 mV, the device exhibited dark current density of 1x10-7 A/cm 2 providing a specific detectivity of 8.2x1012 cm•√Hz/W at 77 K. The LWIR channel has its saturated QE of ~40%, a dark current density of 5.7x10-4 A/cm 2 at -150 mV, exhibiting a specific detectivity value of 1.64x10 11 cm•√Hz/W which stays constant over a broad range of wavelengths.;Finally, we also demonstrated a high-performance SWIR photodetector based on InAs/InAs1-xSbx/AlAs1-xSbx type-II superlattices. The device exhibited 50% cut-off wavelengths of ~1.7 and ~1.8 microm at 200 and 300 K, respectively. The device achieved saturated quantum efficiency values of 36% and 37% at 200 and 300 K, respectively, under front-side illumination and without any AR coating. At 200 K, the device exhibited a dark current density of 1.3x10-8 A/cm2 under -50 mV applied bias providing a specific detectivity of 5.66x10 12 cm•√Hz/W. At 300 K, the device dark current density reaches to 9.6x10-5 A/cm2 under -50 mV bias that provides a specific detectivity of 6.45x10 10 cm•√Hz/W. In addition to the demonstration of high performance MWIR photodetectors and FPA based on InAs/GaSb type-II superlattices, this work also has made it possible for the InAs/InAs 1-xSbx type-II superlattices to become a strong candidate for making high performance multi-spectral infrared imagers and a possible replacement for the current state-of-the-art technologies like InAs/GaSb T2SLs.