Large-Area Planar InGaAs p-i-n Photodiodes With Mg Driven-in by Rapid Thermal Diffusion

Conventional InP/InGaAs/InP heterostructure p-i-n photodiodes (PIN-PDs) are usually fabricated by postgrowth Zn diffusion to form the p-type region. In this letter, we propose a novel method to fabricate the high performance of largearea planar InP/InGaAs/InP PIN-PDs with Mg driven-in process. The Mg driven-in is implemented by spin-on dopant technique using magnesium-silica-film (MgSiO_x) source and through the rapid thermal diffusion. The preparation of MgSiO_x source carrier as the p-type dopant for InP/InGaAs heterostructure is more time-saving than that of zinc-phosphorous-dopant-coating because the latter needs an additional step of oxygen (O₂) plasma to remove a thick resin layer. To improve the responsivity of vertically illuminated PDs, Si/Al₂O₃ bilayers are deposited as the antireflective coating. The 800-μm-diameter PD with Mg driven-in exhibits a low dark current of 20 pA (or 4 nA/cm²) at -10 mV, a high responsivity of 1.14 A/W at 1550-nm wavelength, an excellent quantum efficiency of 91%, and a good uniformity in the light received area. These characteristics are comparable to those of the PD with Zn driven-in.