Opto-electronic devices destined for space must be suitably radiation-hard, meaning that they must be resilient to the effects of high energy radiation in space. For high performance IR (infrared) space-based applications, the current material of choice is MCT (Mercury Cadmium Telluride). MCT is difficult and therefore expensive to fabricate and the constituent materials are becoming increasingly restricted by regulation. The new generation of barrier diode detectors based on III-V materials offer a promising alternative to MCT, providing comparable performance whilst offering devices that are compatible with volume manufacturing processes. As part of a DASA Space-to-Innovate Phase 1 funded project we have developed a novel radiation hard unipolar barrierbased ABaT™ III-V MWIR diode detector. The detector is being subjected to gamma and proton radiation testing to demonstrate its suitability for space environments. To compare the radiation performance of this diode, a number of other typical III-V detector diode structures have been fabricated and tested. In this paper we present the results of the project so far and future plans to develop this into detector arrays.
Inserting an infrared detector architecture into an optical cavity between two high-reflectivity mirrors allows incident light to reflect and pass through the detector multiple times, thereby enhancing absorption within the active region. This allows for a 40-100x thinner optical absorbing region compared to conventional infrared detector structures which reduces the detector dark current and noise and enhances SNR. We report the design, growth, fabrication and characterization of resonant cavity enhanced MWIR photodiodes on GaSb substrates. Devices on GaSb use AlAsSb/GaSb mirrors, AlAsSb spacer layers, and a narrow 96 nm InAsSb absorber. Dark current and detectivity behavior better than equivalent broadband nBn detectors in the literature have been observed. 34nm linewidth detector response is observed. Resonant cavity-enhanced photodiodes with resonant wavelengths of 3.6μm and 3.72μm are demonstrated with dark currents equal to or lower than Rule 07 over the operating temperature range of the device. D* in excess of 1×1010 cm Hz1/2W-1 at 300K and 8×1010 cm Hz1/2W-1 at 250K have been achieved. Amethyst Research has produced packaged resonant-cavity detectors. The 3.6 μm resonant-cavity enhanced photodiode was packaged within an Amethyst Research designed pre-amplifier package with an integrated TEC for detector cooling.