Aligned Carbon Nanotube BioFETs: Toward High-Throughput Single-Molecule Sensing

Abstract

We present the first demonstration of biomolecule detection with Aligned Carbon Nanotube (ACNT) FETs using wafer-scale, high-throughput solution-phase assembled ACNTs. The devices feature a 70 nm gate length and 250 nm width. Unlike previously reported single-molecule CNT bioFETs, based on single-tube fabrication approaches that lack scalability, our approach addresses manufacturability. A key challenge, removal of the solution-processed ACNT wrapping polymer, is tackled using a Transient Assisted Plasma (TAP) clean. We show improved CNT surface cleanliness, as well as improved device performance, and DNA sensing yield. The electrolytic gate reveals the effect of TAP clean without gate oxide interference. Devices show a steep subthreshold swing (SS) <80 mV/dec, and a peak transconductance (gm) >1.3 mS/µm. Binding DNA oligos to CNTs induces a positive shift of the FET threshold voltage (Vth), which serves as the DNA detection signal. Through both real-time and end-point measurements, we obtain a clear signal of >20 mV, on par with Si biofinFETs. Furthermore, we demonstrate the potential of CNT-based bioFETs for single-molecule sensing by projecting signal-to-noise ratios via quantum transport simulations.