Performance and limitations of NIR and extended wavelength eSWIR InP/InGaAs image sensors

In this work we review the reported results as well as the analytical and 3D numerical modeling tools we used to analyze dark current and quantum efficiency data from lattice matched InP/In_0.53Ga_0.47/InP double layer planar 15 μm pixel pitch focal plane arrays (FPAs). These imaging sensors are designed to operate in the near infrared under overcast “Night-Glow” illumination conditions. A notable finding is that the diffusion dark current component is the dominant current component near and above 300 K and is limited by band-to-band radiative recombination processes. The Shockley-Read-Hall (SRH) recombination through band gap states situated at the intrinsic Fermi level is the dominant component for temperatures below 300 K. 3D numerical simulations consisting of both bulk area and perimeter dependent components explains the dark current component of origin in the space charge region (SCR) with an SRH lifetime of τ_SRH = 107 μs. Image sensors with extended cut-off wavelength of 2.5 μm at room temperature built on InP/InGaAs are not lattice matched and needed are reductions in the mismatch throughout the InP/InGaAs multilayer epitaxial structure. We analyzed devices with a buffer layer introduced between the InP and the In_0.81Ga_0.10As absorber and showed that the measured dark current consisted of a diffusion current limited by a back surface interface recombination velocity and a shunt current component expected to be dominant at T ≤ 200 K. At 293 K we calculated a factor of 10 increase in the diffusion current caused by lattice mismatch. Recommended are hole minority carrier lifetime measurements and variable junction diode geometries to assess suspected perimeter/area dependency.