Fig. 1. Schematic diagram of photocurrent measurement system. (a) Schematic representation of system optical path; (b) image of laser focused to tunneling junction device tip

Fig. 2. Characterization of tunneling devices. (a) Optical photo; (b) dark field image; (c) SEM image; (d) STEM-EDS map of tunneling junction device tip

Fig. 3. Results of photocurrent measurement for tunneling junction device. (a) I-V curve trace; (b) time evolution of current without external bias voltage, with laser power of 409 μW, chopper frequency of 1013 Hz, and angle of half-wave plate of 30°; (c) plot of photocurrent as function of laser power, with applied bias of 0 V, chopper frequency of 1013 Hz, and angle of half-wave plate of 30°; (d) plot of normalized photocurrent as function of modulation frequency, with applied bias of 0 V, laser power of 409 μW, and angle of half-wave plate of 30°. Error bars represent level of noise on signal

Fig. 4. Dependence of photocurrent on polarization and applied bias. (a) Plot of photocurrent as function of polarization, with applied bias of 0 V, laser power of 409 μW, and chopper frequency of 1013 Hz; (b) plot of photocurrent as function of applied bias, with laser power of 409 μW, chopper frequency of 1013 Hz, and angle of half-wave plate of 30°. Error bars represent level of noise on signal

Fig. 5. Simulation of electric field and temperature distribution. (a) Simplified model of devices; (b)‒(e) electric field distribution with polarization angle of 0° (b), 30° (c), 60° (d), and 90° (e); (f) relation between electric field enhancement factor and polarization angle; (g) temperature distribution of device in steady state, for which device is placed in air, starting temperature is 300 K, and laser power density is 10⁶ W/m²; (h) time evolution of the highest temperature of device when placed in air