A Graphene/Polycrystalline Silicon Photodiode and Its Integration in a Photodiode-Oxide-Semiconductor Field Effect Transistor.

Yu-Yang Tsai,Chun-Yu Kuo,Bo-Chang Li,Po-Wen Chiu,Klaus Y J Hsu

doi:10.3390/mi11060596

Yu-Yang Tsai, Chun-Yu Kuo + Show 3 more

Open Access

https://doi.org/10.3390/mi11060596

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Journal: Micromachines	Publication Date: Jun 17, 2020
Citations: 3	License type: CC BY 4.0

Affiliation: National Tsing Hua University

Abstract

In recent years, the characteristics of the graphene/crystalline silicon junction have been frequently discussed in the literature, but study of the graphene/polycrystalline silicon junction and its potential applications is hardly found. The present work reports the observation of the electrical and optoelectronic characteristics of a graphene/polycrystalline silicon junction and explores one possible usage of the junction. The current–voltage curve of the junction was measured to show the typical exponential behavior that can be seen in a forward biased diode, and the photovoltage of the junction showed a logarithmic dependence on light intensity. A new phototransistor named the “photodiode–oxide–semiconductor field effect transistor (PDOSFET)” was further proposed and verified in this work. In the PDOSFET, a graphene/polycrystalline silicon photodiode was directly merged on top of the gate oxide of a conventional metal–oxide–semiconductor field effect transistor (MOSFET). The magnitude of the channel current of this phototransistor showed a logarithmic dependence on the illumination level. It is shown in this work that the PDOSFET facilitates a better pixel design in a complementary metal–oxide–semiconductor (CMOS) image sensor, especially beneficial for high dynamic range (HDR) image detection.

Highlights

The unique structural, electronic, and optical properties of graphene have made this two-dimensional material an attractive subject of research in recent years
Using single-layer graphene for vertical optical absorption led to very low photocurrent responsivities [5,6,7,8], normally below or about 10 mA/W, because of the high transparency of graphene over a wide band of light wavelengths [9,10]
For more responsive optical detection in simple planar, single-layer graphene-based photodetectors, a natural way is to construct a hybrid device in which the role of optical absorber is left to other materials in the device and the graphene is used as an efficient conductive material for carrier collection

Summary

Introduction

The unique structural, electronic, and optical properties of graphene have made this two-dimensional material an attractive subject of research in recent years. Using single-layer graphene for vertical optical absorption led to very low photocurrent responsivities [5,6,7,8], normally below or about 10 mA/W, because of the high transparency of graphene over a wide band of light wavelengths [9,10]. A new phototransistor named the PD–oxide–semiconductor field effect transistor (PDOSFET), in which the graphene/poly-Si junction photodiode (PD) is embedded in a conventional metal–oxide–semiconductor field effect transistor (MOSFET), was proposed and experimentally verified Analysis showed that such phototransistor is useful in constructing the pixels in complementary-metal–oxide–semiconductor (CMOS) image sensors for detecting high-contrast images in which the brightness is of high dynamic range (HDR).

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