High-Gain Silicon-Based InGaN/GaN Dot-in-Nanowire Array Photodetector

The characteristics of visible (λ ∼ 550 nm) InGaN/GaN disk-in-nanowire array photoconductive detectors have been measured and analyzed. The nanowire arrays are grown on (001) silicon substrates by plasma-assisted molecular beam epitaxy. Single, elongated quantum dots are formed in the disk regions by strain relaxation. The spectral photocurrent response of the device has been measured as a function of bias and temperature (T ≥ 300 K) and is characterized by multiple distinct peaks, which are believed to arise from electron–hole bound state transitions in the quantum dots. The bias-dependent gain is very large and ∼103, mainly due to a component resulting from the modulation of the conduction volume of the nanowires upon screening of the surface state charge on the walls by photoexcited holes. The temporal photoconductive response of the device has been measured and is characterized by slow (∼seconds) rise and decay times. The measured photocurrent spectra and transient response have been analyzed by appropriate models.