Carrier Transport and Photoresponse in GeSe/MoS₂ Heterojunction p–n Diodes

Abstract

Simple stacking of thin van der Waals 2D materials with different physical properties enables one to create heterojunctions (HJs) with novel functionalities and new potential applications. Here, a 2D material p-n HJ of GeSe/MoS is fabricated and its vertical and horizontal carrier transport and photoresponse properties are studied. Substantial rectification with a very high contrast (>10 ) through the potential barrier in the vertical-direction tunneling of HJs is observed. The negative differential transconductance with high peak-to-valley ratio (>10 ) due to the series resistance change of GeSe, MoS , and HJs at different gate voltages is observed. Moreover, strong and broad-band photoresponse via the photoconductive effect are also demonstrated. The explored multifunctional properties of the GeSe/MoS HJs are expected to be important for understanding the carrier transport and photoresponse of 2D-material HJs for achieving their use in various new applications in the electronics and optoelectronics fields.

Recent Advances in 2D Metal Monochalcogenides

“…Besides this, the clean surface attained in mechanically exfoliated 2D materials makes them more suitable to stack and form good-quality van der Waals heterostructures. [95][96][97] To date, there are few reports on ME of thin layer of 2D MMCs, such as GeS, [98][99][100] GeSe, [101][102][103] SnS, [50,57,104] and SnSe. [36,105,106] Owing to the high interlayer binding energy of MMCs, the exfoliation of an atomically thin single layer is quite difficult.…”

High photoresponsivity and broadband photodetection with a band-engineered WSe2/SnSe2 heterostructure

“…Recently, type-III band alignment has been explored as a platform for tunneling field effect transistors (TFETs) due to its enhanced tunneling current density. 40,[44][45][46][47][48][49] The 2D layered materials based type-III band alignment TFETs with improved responsivity and detectivity have been the focus of many recent studies in the visible wavelengths (e.g. 5.7 A W −1 under 660 nm, 50 244 A W −1 under 550 nm, 51 180 A W −1 under 405 nm 47 ).…”

In‐Plane Optical Anisotropy of Low‐Symmetry 2D GeSe

“…As an isostructural analogue of BP, GeSe also possesses the unique in‐plane anisotropic crystal structure stemmed from its puckered atom structure with two nonequivalent in‐plane crystal directions: armchair and zigzag . With a suitable bandgap (1.14 eV), high absorption coefficient (>10 5 cm −1 ), and high carrier mobility (128.6 cm 2 V −1 s −1 ), GeSe has demonstrated a promising potential in thin‐film solar cells and exhibited an efficiency of 1.48% with good stability .…”

“…For example, Zhai and co‐workers reported a GeSe‐based phototransistor with ultrahigh photoresponsivity of 1.6 × 10 5 A W −1 , about 100 times higher than that of monolayer MoS 2 . In addition to conventional photoconductive photodetectors built on single GeSe nanosheet, vertical p–n heterojunction photodiodes fabricated by stacking p‐type GeSe flakes and n‐type atomically thin 2D materials including WSe 2 and MoS 2 showed excellent performance such as high photoresponsivity of 10 3 –10 4 A W −1 . Besides, the in‐plane anisotropic properties of GeSe including electrical, vibrational, and optical anisotropies as well as its relevant application such as polarization detection have been observed .…”