Bandgap‐Dependent Band‐to‐Band Tunneling in Carbon Nanotube Transistors

ABSTRACT Single‐walled carbon nanotubes (SWCNTs) are considered promising channel materials for post‐Moore nanoelectronics due to their excellent carrier transport properties. However, the intrinsic chirality polydispersity of synthetic SWCNTs leads to significant bandgap non‐uniformity, which fundamentally limits the off‐state performance and integration density of carbon nanotube thin‐film transistors (CNT‐TFTs). Here, we systematically investigate the influence of statistical bandgap distributions on the transport characteristics and leakage mechanisms of CNT‐TFTs using three representative semiconducting SWCNT systems: single‐chirality‐enriched wide‐bandgap (6,5) SWCNTs, mixed‐chirality high‐pressure carbon monoxide (HiPco) SWCNTs with an intermediate average bandgap, and mixed‐chirality arc‐discharge SWCNTs with a smaller average bandgap. We show that narrow‐bandgap SWCNT networks exhibit higher on‐state currents due to reduced Schottky barriers but suffer from pronounced band‐to‐band tunneling (BTBT) under high electric fields, resulting in degraded on/off ratios and subthreshold stability. In contrast, devices based on single‐chirality‐enriched (6,5) SWCNTs effectively suppress BTBT, maintaining ultra‐low off‐state currents (I _off < 10 ⁻¹¹ A) and high on/off ratios (>10 ⁶ ) even at high drain bias. These findings provide a material‐selection guideline for carbon‐based integrated circuits: wide‐bandgap, single‐chirality‐enriched SWCNTs are advantageous for leakage‐sensitive low‐power logic applications, whereas mixed‐chirality SWCNT networks with smaller average bandgaps are more suitable for high‐drive‐current analog and radio‐frequency electronics.