Graphene and Thin-Film Semiconductor Heterojunction Transistors Integrated on Wafer Scale for Low-Power Electronics

Graphene heterostructures in which graphene is combined with semiconductors or other layered 2D materials are of considerable interest, as a new class of electronic devices has been realized. Here we propose a technology platform based on graphene–thin-film-semiconductor–metal (GSM) junctions, which can be applied to large-scale and power-efficient electronics compatible with a variety of substrates. We demonstrate wafer-scale integration of vertical field-effect transistors (VFETs) based on graphene–In–Ga–Zn–O (IGZO)–metal asymmetric junctions on a transparent 150 × 150 mm² glass. In this system, a triangular energy barrier between the graphene and metal is designed by selecting a metal with a proper work function. We obtain a maximum current on/off ratio (<i>I</i>_on/<i>I</i>_off) up to 10⁶ with an average of 3010 over 2000 devices under ambient conditions. For low-power logic applications, an inverter that combines complementary n-type (IGZO) and p-type (Ge) devices is demonstrated to operate at a bias of only 0.5 V

Tuning Carrier Tunneling in van der Waals Heterostructures for Ultrahigh Detectivity

Semiconducting transition metal dichalcogenides (TMDs) are promising materials for photodetection over a wide range of visible wavelengths. Photodetection is generally realized via a phototransistor, photoconductor, p–n junction photovoltaic device, and thermoelectric device. The photodetectivity, which is a primary parameter in photodetector design, is often limited by either low photoresponsivity or a high dark current in TMDs materials. Here, we demonstrated a highly sensitive photodetector with a MoS₂/h-BN/graphene heterostructure, by inserting a h-BN insulating layer between graphene electrode and MoS₂ photoabsorber, the dark-carriers were highly suppressed by the large electron barrier (2.7 eV) at the graphene/h-BN junction while the photocarriers were effectively tunneled through small hole barrier (1.2 eV) at the MoS₂/h-BN junction. With both high photocurrent/dark current ratio (>10⁵) and high photoresponsivity (180 AW^–1), ultrahigh photodetectivity of 2.6 × 10¹³ Jones was obtained at 7 nm thick h-BN, about 100–1000 times higher than that of previously reported MoS₂-based devices

Graphene for True Ohmic Contact at Metal–Semiconductor Junctions

The rectifying Schottky characteristics of the metal–semiconductor junction with high contact resistance have been a serious issue in modern electronic devices. Herein, we demonstrated the conversion of the Schottky nature of the Ni–Si junction, one of the most commonly used metal–semiconductor junctions, into an Ohmic contact with low contact resistance by inserting a single layer of graphene. The contact resistance achieved from the junction incorporating graphene was about 10^–8 ∼ 10^–9 Ω cm² at a Si doping concentration of 10¹⁷ cm^–3