Recently a group from University of Virginia, demonstrated InAlAsSb digital alloy APDs operating in the 1-2 μm wavelengths with a very low excess noise, equivalent to silicon APDs. With a digital-alloy In0.3Al0.7AsSb multiplier, the excess noise is similar to that of Si APDs and the impact ionization parameter k is about 0.02 at gains >10. Using this digital alloy detector technology, our modeling calculations show that a noise equivalent power (NEP) comparable to HgCdTe APD receivers can be achieved at TE-cooled temperatures. Acqubit has designed and developed a 1 GHz receiver operating at -30°C using the InAlAsSb digital alloy APD designed for 2 μm wavelength operation. We measured an NEP of 600 fW/√Hz at 1.5 μm wavelength. In this presentation, we will present the receiver design and characterization results and modeling data to show the potential to achieve high sensitivity comparable to HgCdTe and Si receivers.
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