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In applications where high sensitivity is required, the internal gain mechanism of avalanche photodiodes can provide a performance advantage relative to p-i-n photodiodes. However, this internal gain mechanism leads to an excess noise that scales with gain. This excess noise term can be minimized by using materials systems in which impact ionization is initiated primarily by one carrier type. Recently, two Sb-based materials systems, AlInAsSb and AlGaAsSb, have exhibited exceptionally low excess noise, particularly for III–V compound materials. There are four important considerations that can impact the excess noise measurements in such low-noise materials. These considerations deal with the excess noise factor calculation method, measurement RF frequency, measurement wavelength, and the gain calculation method. In this paper, each of these factors is discussed, and their implications on excess noise are considered.

Mid-IR is a useful wavelength range for both science and military applications due to its low atmospheric attenuation and ability to be used for passive detection. However, many solutions for detecting light in this spectral region need to be operated at cryogenic temperatures as their required narrow bandgaps suffer from carrier recombination and band-to-band tunneling at room temperature leading to high dark currents. These problems can be alleviated by using a separate absorption, charge, and multiplication avalanche photodiode. We have recently demonstrated such a device with a 3-µm cutoff using Al0.15In0.85As0.77Sb0.23, as the absorber, grown on GaSb. Here we investigate Al0.15In0.85As0.77Sb0.23 as a simple PIN homojunction and provide metrics to aid in future designs using this material. PL spectrum measurements indicate a bandgap of 2.94 µm at 300 K. External quantum efficiencies of 39% and 33% are achieved at 1.55 µm and 2 µm respectively. Between 180 K and 280 K the activation energy is ∼0.22 eV, roughly half the bandgap of Al0.15In0.85As0.77Sb0.23, indicating thermal generation is dominant.

We report InGaAs/InP based p-i-n photodiodes with an external quantum efficiency (EQE) above 98% from 1510 nm to 1575 nm. For surface normal photodiodes with a diameter of 80 µm, the measured 3-dB bandwidth is 3 GHz. The saturation current is 30.5 mA, with an RF output power of 9.3 dBm at a bias of −17 V at 3 GHz.