Chapter 7 - Carbon Nanotube Schottky Photodiodes

Abstract

This chapter deals with the fabrication and investigation of carbon nanotubes-based Schottky photodiodes using different metals and structures. It is found that the work functions of metals play an important role in determining the properties of the photodiodes. Symmetric Schottky photodiodes using different metals have varied dark current and photocurrent of several orders of magnitude. Low built-in potentials resulted in large dark current and photocurrent, while high built-in potentials caused smaller dark current and photocurrent. Two Schottky barriers reversely connecting with each other in the symmetric metal structure, which was verified by position-dependent photocurrent measurements, can explain this. In order to improve the performance of CNT-based Schottky photodiodes, asymmetric structure photodiodes using metals with high/low work functions at two contacts were fabricated. Compared to the symmetric photodiodes, asymmetric photodiodes had lower dark current and higher photocurrent.