Large-Area Planar Wavelength-Extended InGaAs p-i-n Photodiodes Using Rapid Thermal Diffusion With Spin-On Dopant Technique

In this letter, we report the large-area planar-type 2.2-μm wavelength-extended InAsP/InGaAs/InAsP p-i-n photodetectors (PDs) using the rapid thermal diffusion (RTD) technique. The zinc-phosphorous-dopant-coating was used as the spin-on dopant source, which was driven into the InAsP/InGaAs heterostructure to form the p-type cap layer of p-i-n diode through the RTD process. The Si/Al₂O₃ bilayers were deposited as the antireflective coating to improve the responsivity of vertically illuminated the PDs. The 800-μm-diameter PD exhibits a low dark current of 4.1 × 10^-8 A (8.2 × 10^-6 A/cm²) at -10 mV, a cutoff wavelength of 2.2 μm, a quantum efficiency of above 90% in the wavelength range of 1.4-2.0 μm, and a high responsivity of 1.45 A/W at 2-μm wavelength at room temperature. In addition, the PD exhibits good uniformity in the light received area in the illuminated power range of 0.1-2.0 mW.