Enhanced photoresponse in MoTe2 photodetectors with asymmetric graphene contacts

TL;DR

This study demonstrates that asymmetric graphene contacts on multilayer MoTe2 create a strong built-in electric field, enabling broad-spectrum, fast, and self-powered photodetection suitable for low-power optoelectronic devices.

Contribution

The paper introduces a novel approach using asymmetric graphene contacts to enhance photoresponse in MoTe2 photodetectors, achieving broadband detection and fast response without external bias.

Findings

Large built-in electric field (~100 kV/cm) across MoTe2 channel.

Broadband photoresponse from 400 to 1400 nm.

Fast photoresponse time of approximately 0.01 ms.

Abstract

Atomically thin two dimensional (2D) materials are promising candidates for miniaturized high-performance optoelectronic devices. Here, we report on multilayer MoTe2 photodetectors contacted with asymmetric electrodes based on n- and p-type graphene layers. The asymmetry in the graphene contacts creates a large (Ebi ~100 kV cm-1) built-in electric field across the short (l = 15 nm) MoTe2 channel, causing a high and broad (400 to 1400 nm) photoresponse even without any externally applied voltage. Spatially resolved photovoltage maps reveal an enhanced photoresponse and larger built-in electric field in regions of the MoTe2 layer between the two graphene contacts. Furthermore, a fast (~0.01 ms) photoresponse is achieved in both the photovoltaic and photoconductive operation modes of the junction. Our findings could be extended to other 2D materials and offer prospects for the implementation of asymmetric graphene contacts in future low-power optoelectronic applications.