An Ultralow Power Mixed Dimensional Heterojunction Transistor Based on the Charge Plasma pn Junction

Development of a reliable doping method for 2D materials is a key issue to adopt the materials in the future microelectronic circuits and to replace the silicon, keeping the Moore's law toward the sub-10 nm channel length. Especially hole doping is highly required, because most of the transition metal dichalcogenides (TMDC) among the 2D materials are electron-doped by sulfur vacancies in their atomic structures. Here, hole doping of a TMDC, tungsten disulfide (WS₂) using the silicon substrate as the dopant medium is demonstrated. An ultralow-power current sourcing transistor or a gated WS₂ pn diode is fabricated based on a charge plasma pn heterojunction formed between the WS₂ thin-film and heavily doped bulk silicon. An ultralow switchable output current down to 0.01 nA µm⁻¹, an off-state current of ≈1 × 10⁻¹⁴ A µm⁻¹, a static power consumption range of 1 fW µm⁻¹–1 pW µm⁻¹, and an output current ratio of 10³ at 0.1 V supply voltage are achieved. The charge plasma heterojunction allows a stable (less than 3% variation) output current regardless of the gate voltage once it is turned on.