Voltage-switchable photocurrents in single-walled carbon nanotube-silicon junctions for analog and digital optoelectronics

Recent progress in silicon photonics has dramatically advanced the possible realization of heterogeneous logic circuits. A variety of Boolean optoelectronic circuits have been proposed. In this context, experimental investigation of logic operations with both optical and electrical inputs in chip-integrable devices is highly desirable. Here, we present a new kind of photodiode-based logic device using scalable heterojunctions of carbon nanotubes and silicon, the output currents of which can be manipulated completely by both optical and electrical inputs. This provides a novel platform for heterogeneous optoelectronic logic elements with voltage-switchable photocurrent responsivity of >1 A W -1, photovoltage responsivity of >1 × 10 5 V W -1, electrical on/off ratios of >1 × 10 5 and optical on/off ratios of >1 × 10 4. To demonstrate their scalability, we fabricated a large array of photoactive elements on a centimetre-scale wafer. We also present bidirectional phototransistors and novel clock-triggerable logic elements such as a mixed optoelectronic AND gate, a 2-bit optoelectronic ADDER/OR gate and a 4-bit optoelectronic digital-to-analog converter.