High-performance near-infrared photodetectors based on gate-controlled graphene–germanium Schottky junction with split active junction

Cihyun Kim,Byoung Hun Lee,Kyoung Eun Chang,Hyeon Jun Hwang,Tae Jin Yoo,Min Gyu Kwon

doi:10.1515/nanoph-2021-0738

Abstract

Abstract The structure of a gate-controlled graphene/germanium hybrid photodetector was optimized by splitting the active region to achieve highly sensitive infrared detection capability. The strengthened internal electric field in the split active junctions enabled efficient collection of photocarriers, resulting in a responsivity of 2.02 A W−1 and a specific detectivity of 5.28 × 1010 Jones with reduced dark current and improved external quantum efficiency; these results are more than doubled compared with the responsivity of 0.85 A W−1 and detectivity of 1.69 × 1010 Jones for a single active junction device. The responsivity of the optimized structure is 1.7, 2.7, and 39 times higher than that of previously reported graphene/Ge with Al2O3 interfacial layer, gate-controlled graphene/Ge, and simple graphene/Ge heterostructure photodetectors, respectively.

Highlights

Various graphene/semiconductor Schottky junction photodetectors have been investigated to combine the benefitsZeng et al demonstrated a graphene/Ge Schottky junction-based infrared photodetector with a responsivity of 51.8 mA W−1 operating at zero bias voltage [13]
The graphene/Ge junction photodetectors have a comparatively smaller gain than graphene/Si junction photodetectors, and the responsivity remains limited due to low external quantum efficiency (EQE) of 60% because of the long transit time of the minority carrier in the depletion region of Ge [12, 15]. These results suggest that a primary problem with a gatecontrolled graphene/Ge Schottky junction photodetector is the inefficient transport of photogenerated carriers
The dark currents of both devices had the characteristics of a typical Schottky junction and were substantially modulated by the gate bias (Figure 2A and B, black lines)

Summary

Introduction

Zeng et al demonstrated a graphene/Ge Schottky junction-based infrared photodetector with a responsivity of 51.8 mA W−1 operating at zero bias voltage [13]. The graphene/Ge junction photodetectors have a comparatively smaller gain than graphene/Si junction photodetectors, and the responsivity remains limited due to low external quantum efficiency (EQE) of 60% because of the long transit time of the minority carrier in the depletion region of Ge [12, 15]. These results suggest that a primary problem with a gatecontrolled graphene/Ge Schottky junction photodetector is the inefficient transport of photogenerated carriers. This result is 1.7–39 times higher than the previouslyreported responsivity of a graphene/Ge photodetector

Experimental details

Results and discussion

10-5 Figure 2

Conclusions