Effect of the Passivation Layer on the Noise Characteristics of Mid-Wave-Infrared InAs/GaSb Superlattice Photodiodes

The authors describe the noise characterization of a mid-wavelength-infrared (MWIR) photodiode based on indium arsenide and gallium antimonide (InAs/GaSb) superlattice (SL), addressing the influence of different passivation layers applied to the surface of the device. The MWIR InAs/GaSb SL design structure is based on p-i-n configuration grown by the molecular beam epitaxy on a (001) n-GaSb substrate. The SiO₂-passivated SL photodiodes demonstrated a Schottky-limited noise up to a bias voltage of -0.1 V where the measured peak responsivity is 1.37 AAV with a cut-off wavelength of 4.9 μm and the specific detectivity as high as 1.23 × 10¹² cm. Hz^1/2 /W, demonstrating the high quality of the fabricated MWIR SL photodiodes. The noise measurements exhibited a frequency-dependent plateau (i.e., 1/f noise) for unpassivated and Si₃N₄-passivated samples, whereas 1/f-type noise suppression (i.e., frequency-independent plateau) with a noise current reduction at about 30 Hz of more than one order of magnitude was observed for the SiO₂-passivated ones.