Fundamental Study on Silicon Optical Switch for Total-Silicon Opto-Electric Integrated Circuits

点击翻译按钮获取中文摘要

The purpose of this study is an implementation of optical switch based on infra-red light absorption with free carriers in silicon. This is not ever proposed and a very challenging target. Since one of key issues to realize that is how large amount of free carriers is generated, a comb-shaped MOS transistor is fabricated. Due to reasons described below, the first trial failed however, a new comb-shaped MOS transistor is realized and future targets can be fixed based on analyses on optical wave guide structure.<Reasons of failure of first trial>1. Incident parallel infra-red light of 10 μm in diameter does not stay within a beam of 1 μm in height and 1 mm in length but disperse into silicon substrate.2. Polysilicon with 10^<21>/cm^3 impurity, filled into comb gaps, strongly absorbs incident infrared light.<Realization of comb-shaped transistor>1. A comb-shaped transistor of 2 μm in effective channel length with 1-μm high and 50-nm wide beams is successfully obtained.2. A comb-shaped transistor having 31 beams realizes 5-times greater drivability compared to that of planar transistor.<Further investigations>1. Incident infra-red light should be locked up inside silicon beam having higher refractive index using SOI substrate.2. ITO gate should be utilized. However, since the less conductivity of the ITO gives less absorption, it is estimated that the gate conductivity should be optimized.3. Since it is analyzed that high reflective metal films like aluminum can be suitable, aluminum-gate MOS transistors will be implemented as well as the ITO transistors.4. Based on the experimental and the analyses described above, it is still planned to realize an optical silicon switch MOS transistor.