A CMOS-Compatible Photonic Demodulator With Low-Power Consumption for Time-of-Flight Image Sensor

Abstract

This article presents a CMOS-compatible low-power photonic demodulator for time-of-flight (ToF) CMOS image sensor. The proposed device called the junction-assisted photonic demodulator (JAPD) uses electric field applied through two guide electrodes to facilitate the collection of optically generated minority carriers but using a p-n junction to prevent direct majority carrier current. A prototype of the JAPD has been fabricated in a 0.18- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> standard CMOS foundry process. Experimental results show that it can achieve a low-power consumption of 29 fW per pixel and a high modulation contrast (MC) of 98%. Through process optimization, it is shown that the optical window can be fully depleted during the demodulation process. In TCAD simulation, the frequency response can be significantly improved by ensuring full depletion of the optical window.