Mid Wavelength Infrared Resonant Cavity Enhanced Photodiodes For Infrared Spectroscopic Sensing Of Chemicals And Other Narrow-Band Optical Signals

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. 34 nm linewidth detector response is observed. Resonant cavity-enhanced photodiodes with resonant wavelengths of 3.6 mu m and 3.72 mu m are demonstrated with dark currents equal to or lower than Rule 07 over the operating temperature range of the device. D* in excess of 1x10(10) cm Hz(1/2)W(-1) at 300K and 8x10(10) cm Hz(1/2)W(-1) at 250K have been achieved. Amethyst Research has produced packaged resonant-cavity detectors. The 3.6 mu m resonant-cavity enhanced photodiode was packaged within an Amethyst Research designed pre-amplifier package with an integrated TEC for detector cooling.