Programmable WSe2/Ge Heterojunction Field‐Effect Transistor with Visible‐Infrared Wavelength‐Distinguishing Detection Capability

Abstract

Abstract Programmable devices can be easily switched between n‐type and p‐type devices by applying an electric field and are promising candidates for simplifying the currently used fabrication process and increasing programmable flexibility. This paper proposes a 2D WSe2/3D Ge heterojunction field‐effect transistor (JFET) with a top metal‐insulator semiconductor gate. The n‐type and p‐type JFETs are realized based on one device structure; furthermore, the n‐type JFET can be converted into p‐type and vice versa under the control of top‐gate voltages of different polarities. The nJFET and pJFET has low subthreshold swings of 102 and 65 mV dec−1 with a high on/off ratio of ≈105, respectively. Moreover, a visible‐infrared wavelength‐distinguishing photodetector is implemented based on this device. It exhibits a bidirectional photoresponse, wherein the photocurrent polarity is reversed depending on the wavelength of light. Under illumination at 532 nm, positive photoresponsivity is realized through the effective charge separation of the heterojunction. In contrast, the JFET has a negative photoresponsivity at an infrared wavelength of 1550 nm, which is related to type‐I band alignment and the photogating effect. These results indicate that the device has promising potential as a multifunctional optoelectronic device.

Keywords

• 2D/3D heterostructure
• junction field‐effect transistors
• programmable device
• visible‐infrared photodetector
• wavelength‐distinguishing