Fig. 1. (a) Device A heterostructure and energy band diagram in the pinch-off condition (b) at the onset of illumination and (c) under steady-state illumination. (d) Device B heterostructure and energy band diagram in the pinch-off condition (e) at the onset of illumination and (f) under steady-state illumination. (g) Device C heterostructure and energy band diagram in the pinch-off condition (h) at the onset of illumination and (i) under steady-state illumination.

Fig. 2. AFM image of GaN nanodots after size reduction and prior to AlGaN barrier overgrowth. The image size is 2  μm×2  μm.

Fig. 3. IDS−VDS data for Device A showing good transistor action with inclusion of GaN nanodots.

Fig. 4. Transfer characteristics for Device A in the dark and under UV illumination. The device shows good pinch-off in the dark and switches to an on-state under UV illumination.

Fig. 5. Transient response under 4.70 eV illumination and use of an electrical fill pulse to rapidly reset the detector.

Fig. 6. Responsivity spectrum for a 40 ms rise time for Device A at different optical intensities. Inset shows the same data on a linear scale.

Fig. 7. Transfer characteristics for Device B in the dark and under UV illumination. Despite the incomplete pinch-off, the device exhibited large ΔIDS.

Fig. 8. Responsivity spectrum for a 40 ms rise time for Device B.

Fig. 9. Responsivity and bandwidth under 4.35 eV illumination for Device B under different optical intensities.

Fig. 10. Transfer characteristics for Device C in the dark and under UV illumination.

Fig. 11. Responsivity for Device C for a 40 ms rise time.