Wide-wavelength and low-dark-current lattice-mismatched GaInAs photodiodes

A lattice-mismatched GaInAs photodiode with low dark current and very wide-wavelength spectral response has been fabricated on InP substrate. The uses of a lattice-mismatched GaInAs light-absorbing layer and a very thin InP cap layer provide extended responsivity for longer and shorter wavelengths, respectively. To improve the crystal quality of the lattice-mismatched GaInAs layer a strained-superlattice buffer layer was used, with a combined thermal cycle annealing process, resulting in a low dark current. The shallow p-n junction of the photodiode was formed by a newly developed Zn diffusion technique.