Preparation Of Two-Dimension Semiconductor WSe₂ Based Heterojunction/Homojunction And Its Photoelectric Properties

Lateral homojunctions made of two-dimensional(2D)layered materials are promising for optoelectronic and electronic applications.Here,we first studied the lateral WSe₂-WSe₂homojunction photodiodes formed spontaneously by thickness modulation,in which there are unique band structures of a unilateral depletion region.The electrically tunable junctions can be switched from n-n to p-p diode,and the corresponding rectification ratio increases from about 1 to 1.2×10⁴.In addition,in the photovoltaic mode,the device shows a strong optical response,and the large open-circuit voltage of 0.49 V and short-circuit current of 0.125 n A can be obviously observed.Besides,due to the unilateral depletion region,the diode can achieve a high detectivity of 4.4×10¹⁰Jones and a fast photoresponse speed of 0.18 ms in self-drive mode(V_g=0,V_ds=0).The studies not only demonstrated the great potential of the lateral homojunction photodiodes for self-power photodetector,but also allowed for the development of other functional devices,such as,a non-volatile programmable diode for logic rectifiers.However,due to the high intensity of recombination and the lack of internal optical gain mechanism,the WSe₂-WSe₂ homojunction photodetector has low photocurrent and response rate.Through previous research we found that the type?band alignment of the van der Waals heterojunction has obtained wide attention due to tunneling mechanism.This tunneling mechanism may maintain a low dark current while bringing a large optical gain,effectively improving the photocurrent and responsiveness.So,in order to solve this problem,we design a broken-gap vd W heterojunction WSe₂/PtS₂with a bilateral accumulation region and a big band offset by utilizing both thick PtS₂ as an effective carrier selective contact and bipolar WSe₂as an effective backgated control layer.At room temperature,the device exhibits excellent electrical properties,with current on/off ratio and rectification ratio reaching 10⁸ simultaneously.On the other hand,due to the light-induced tunneling mechanism and the ultra-low dark current,the photocurrent on/off ratio of WSe₂/PtS₂tunneling heterodiodes exceeds 10⁵,and the responsivity and detectivity are nearly 100 times higher than that of WSe₂/WSe₂lateral homojunction photodetector.In addition,due to the energy band design of the bilateral accumulative layer and optical tunneling mechanism,the interface capture effect is greatly suppressed,effectively improves the response speed of the photodetector,and reduces the response time to 8?s.The proposed heterojunction demonstrating not only the high-performance tunneling diode but also provides in-depth understanding of tunneling mechanism in the development of the future electronic and optoelectronic applications.