High-performance room temperature 2.75 µm cutoff In_0.22Ga_0.78As_0.19Sb_0.81/Al_0.9Ga_0.1As_0.08Sb_0.92 avalanche photodiode

Extended shortwave infrared (eSWIR) detectors capable of detecting wavelengths between 1.7 and 2.7 µm are useful for a wide range of applications, such as remote sensing and monitoring, but most of these detectors require cooling to reduce the dark currents. Identifying a suitable material that extends the wavelength range to well beyond 2 µm with minimal cooling is therefore important. The overall sensitivity of such a detector can be enhanced by using it in conjunction with a wide bandgap multiplication region which can increase the photocurrent via impact ionization. In this work, a systematic study of avalanche multiplication in seven Al0.9Ga0.1As0.08Sb0.92 diodes lattice matched to GaSb shows that the electron impact ionization coefficient (α) is larger than the hole impact ionization coefficient (β), especially at low electric fields. Using In0.22Ga0.78As0.19Sb0.89 (bandgap=0.45eV) as the absorber and Al0.9Ga0.1As0.08Sb0.92 (bandgap=1.6eV) as the multiplier in a separate absorption, charge, and multiplication region avalanche photodiode configuration enabled room temperature optical detection up to 2.75 µm with a peak external quantum efficiency (EQE) of >50% at the punch-through voltage (Vpt) ∼2µm wavelength. This device demonstrates a low excess noise of F=4.5 at a multiplication of M=20, giving rise to a noise equivalent power for an unoptimized device of 1.69×10−12W/Hz. A maximum multiplied EQE of >2000% at 2 µm is achieved before a low breakdown voltage of 18.9 V, obtained using a novel undepleted absorber design. This work shows the possibility of a high sensitivity eSWIR detector capable of operating at room temperature.