Low excess noise Al0.8In0.2As0.31Sb0.69 avalanche photodiodes lattice matched to InAs

Indium arsenide (InAs) is an exceptional material for absorbing infrared photons with wavelengths up to 3500 nm, making it ideal for mid-infrared detection. However, the development of high-performance separate sbsorption and multiplication avalanche photodiodes (SAM APDs) has been hindered by the absence of suitable low-noise avalanche materials compatible with InAs absorbers. In this study, we investigate the potential of Al 0.8 In 0.2 As 0.31 Sb 0.69 (lattice matched to InAs) as a low-noise avalanche material. We have performed comprehensive Al 0.8 In 0.2 As 0.31 Sb 0.69 excess noise measurements using three optical signal wavelengths on a large number of p-i-n and n-i-p diodes. Under pure electron injection, Al 0.8 In 0.2 As 0.31 Sb 0.69 p-i-n diodes exhibit very low excess noise factors ~4 at high gain of 100, corresponding to an effective k of 0.030.03. In contrast, a small gain of 3 produces very high excess noise factors (>17) when using hole injection in the n-i-p diodes. The contrasting behavior indicates that in Al 0.8 In 0.2 As 0.31 Sb 0.69 electron ionization coefficient is much larger than hole ionization coefficient. As a consequence, low-noise Al 0.8 In 0.2 As 0.31 Sb 0.69 avalanche regions emerge as a promising candidate for the avalanche region of SAM-APDs designed for mid-infrared applications, such as methane gas sensing and imaging through fog. The design of such SAM-APDs should ensure electrons rather than holes are injected into the Al 0.8 In 0.2 As 0.31 Sb 0.69 avalanche regions to achieve the lowest possible excess noise factors.