Ion implantation enhanced metal–Si–metal photodetectors

The quantum efficiency and frequency response of simple Ni-Si-Ni metal-semiconductor-metal (MSM) photodetectors at long wavelengths are significantly enhanced with a simple, ion-implantation step to create a highly absorbing region /spl sim/1 /spl mu/m below the Si surface. The internal quantum efficiency is improved by a factor of /spl sim/3 at 860 nm (to 64%) and a full factor of ten at 1.06 /spl mu/m (to 23%) as compared with otherwise identical unimplanted devices. Dark currents are only slightly affected by the implantation process and are as low as 630 pA for a 4.5-/spl mu/m gap device at 10-V bias. Dramatic improvement in the impulse response is observed, 100 ps vs, 600 ps, also at 10-V bias and 4.5-/spl mu/m gap, due to the elimination of carrier diffusion tails in the implanted devices. Due to its planar structure, this device is fully VLSI compatible. Potential applications include optical interconnections for local area networks and multi-chip modules. >