Heterogeneous integration of an InAs nanowire with energy-efficient CMOS delta-sigma modulator

A nanowire-CMOS heterogeneously integrated circuit is demonstrated. The circuit consists of a voltage divider using series-connected resistors and a delta-sigma modulator (DSM); a single InAs nanowire is used as one of the resistors. Nanowire deposition is carried out by field-assisted self-assembly (FASA) process based on dielectrophoresis. The DSM uses a class-C inverter in its loop filter instead of an opamp to obtain high energy efficiency, and successfully converts the voltage across the nanowire into density-modulated digital pulses. The present result suggests that variations in the nanowire resistance caused, for example, by chemical absorption on the nanowire surface can be sensed and converted into the digital output.