Defect Reconstruction Triggered Full-Color Photodetection in Single Nanowire Phototransistor

Abstract

The coherent developments of high performance broadband photodetection and a discrimination technique are highly essential for multiscene imaging and optical communication applications. The integration of traditional bandpass filters or stacking other spectral absorber in photodetectors often complicates the device design and leads to asymmetric photogain for each waveband. Herein, we report on ultraviolet–visible (UV-vis) multispectral photodetection based on a single ZnO nanowire (NW) phototransistor, where defect reconstructions can be reliably induced by a two-step annealing that leads to the observed broadband photodetection. Electron paramagnetic resonance and photoluminescence spectra reveal the reconstructions of zinc-atom-related defects (i.e., zinc interstitials and vacancies). Combined microdifferential reflectance and multimode scanning probe microscope (SPM) technique confirm the presence of a unique visible-sensitive Zn-rich ZnO shell layer and a trap-free UV-sensitive ZnO core. We achieve not only an ultrahigh carrier mobility (212.4 cm2 V–1 s–1), but also a concurrent improvement for UV-vis photodetection with superior responsivities and detectivities on the orders of 105 AW–1 and 1015 Jones at 100 mV, respectively, and response speeds less than one second. Moreover, photocurrents under blue, green, and red stimuli can be selectively switched on/off by tuning the gate stress. These high performances in all figures of merit have opened new routes to tailor intrinsic properties of a single NW for optoelectronic applications.