Low excess noise and high quantum efficiency avalanche photodiodes for beyond 2 μm wavelength detection

The rising concentration of greenhouse gases, especially methane and carbon dioxide, is driving global temperature increases and exacerbating the climate crisis. Monitoring these gases requires detectors that operate in the extended short-wavelength infrared range (similar to 2.4 mu m), covering methane (1.65 mu m) and carbon dioxide (2.05 mu m) wavelengths. Here, we present a high-performance linear mode avalanche photodetector (APD) with an InGaAs/GaAsSb type-II superlattice absorber and an AlGaAsSb multiplier, matched to InP substrates. This APD achieves a room temperature gain of 178, an external quantum efficiency of 3560% at 2 mu m, low excess noise (less than 2 at gains below 20), and a small temperature coefficient of breakdown (7.58 mV/K center dot mu m). These results indicate that a manufacturable semiconductor material-based APD could significantly advance high-sensitivity receivers for greenhouse gas monitoring, potentially enabling their commercial production and widespread use.