Silicon Electro-Optic Modulators Using Quantum Tunneling Structures

Injection-type silicon electro-optic modulators are widely used in onchip optical interconnections due to its high modulation efficiency. However, as the modulator dimension approaches the wavelength limit, it becomes hard to improve the modulator speed by shrinking the device. A new approach to further scale down the dimension of an intrinsic device in injection-type electro-optic modulators without suffering from subwavelength confinement problem is proposed. The device consists of stacked PN or PiN cells connected by tunneling structures to enable current conduction. The diffusion capacitance is reduced due to the reduction of quasi-neutral region width in each device. In this paper, a detail study is given to the case of a two-cell modulator. A twofold of capacitance reduction and speed improvement are observed. Further speed improvement is expected by splitting the modulator into more cells, and the simulation approach for the tunneling structures in such an optical device is also discussed in details.