Planar InGaAs p-i-n Photodiodes With Transparent-Conducting-Based Antireflection and Double-Path Reflector

In this letter, we report on the design of large-area planar InP/InGaAs/InP heterostructure p-i-n photodiodes (PIN-PDs) with gallium-doped zinc oxide (GZO)/SiO_x antireflective bilayer and AuGe/Au double-path reflectors for the enhancement in the position sensitivity and device response. The heavily GZO layer was grown on top of the InGaAs PIN-PDs by plasma-mode atomic layer deposition to improve the lateral resistance effect. The GZO/SiO_x antireflection (AR) exhibits an average optical reflectance of below 5% in the infrared (IR) spectrum. Then, the combination of two features of AR coating and double-path reflector is employed to decrease incident light loss and increase double-path absorption. The dark current is less than several nanoamperes and the breakdown voltage is higher than 40 V reverse bias for the large-area InGaAs diode with 750- μm-diameter region. The device responsivity is 1.0 and 1.2 A/W at 1310-and 1550-nm wavelengths, respectively. Under the light illumination of 1550-nm wavelength, the photosensitivity shows good uniformity in the light-received area. The quantum efficiency is higher than 90% in the whole IR region, and the cutoff wavelength is 1650 nm.