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A high-performance AlGaN/GaN-based ultraviolet photodetector with a field-enhanced mechanism for photocurrent collection is designed and fabricated in this work. In addition to the inherent polarization field, two additional sets of collection fields are formed from a 2DEG layer to a ITO thin film and from the 2DEG layer to a cathode electrode sinker. The effectiveness in the collection of photogenerated carriers is remarkably enhanced, which leads to a photocurrent of 6.6 mA/mm under the illumination of 365 nm-centered ultraviolet light at an intensity of 1.8 mW/cm2. With an in-built shallow isolation trench, the dark current is suppressed below 40 pA/mm under a device bias of 5.0 V. A photo-to-dark current ratio as high as 1.7 × 108, a record high photo-responsivity over 4.3 × 106 A/W, and a high gain of 1.46 × 107 under 365-nm light are demonstrated by the fabricated prototype, showing great competitiveness in state-of-the-art AlGaN/GaN-based ultraviolet photodetectors. [ABSTRACT FROM AUTHOR]

Ferroelectric (Pb0.97,La0.03)(Zr0.52,Ti0.48)O3 thin films in different thicknesses were fabricated on Pt/Ti/SiO2/Si substrates through a sol-gel process. Film thickness dependence of photoinduced current was investigated under the illumination of ultraviolet light. A theoretical model was developed to describe the thickness-dependent photocurrent. Both the theoretical model and experimental results showed that the photocurrent increases exponentially with the decrease in film thickness. However, photocurrent may drop in the films with the very small thickness of tens of nanometers and below in which the small size effect of ferroelectricity is considered. This model also reveals the relationship between the photocurrent and the internal electric field or remnant polarization and predicts a small diffusion current in the opposite direction at very low field or polarization region. These results provide useful guides for the design of ferroelectric film photovoltaic devices. [ABSTRACT FROM AUTHOR]

The stability and magnitude of photovoltage response in (Pb0.97La0.03)(Zr0.52Ti0.4g)O_3 (PLZT) ferroelectric thin films were investigated in the present work. Photovoltage degrading in multi-cycle ultraviolet (UV) light illumination was observed in Au/PLZT/Pt sandwich capacitor configuration and in-plane polarized configuration with a pair of top Au interdigital electrodes. For the in-plane polarized configuration, which had a greatly enhanced electrode gap, the reduction ratio of photovoltage during multi-cycle UV illumination was significantly smaller hence the stability of photovoltage was greatly improved over the sandwich capacitor configuration. Trapping of photo-induced charges and polarization screening at the ferroelectric-electrode interfaces were found to be the major cause for the degrading of photovoltage in ferroelectric films. Furthermore, for the Au/PLZT/Pt capacitor, the magnitude and even the polarity of the photovoltage were remarkably affected by the asymmetric interfacial Schottky barriers due to the small photovoltage magnitude determined by the small film thickness. [ABSTRACT FROM AUTHOR]

Photovoltaic effect in ferroelectric thin films with thickness below 100 nm was investigated through both theoretical and experimental approaches. Unprecedented high photovoltaic power conversion efficiency around ∼0.28% was achieved with epitaxial (Pb0.97La0.03)(Zr0.52Ti0.48)O3 ferroelectric thin films, which is about 2 orders of magnitude higher than the reported in literature for ferroelectrics. Theoretical analysis indicated that efficiency can be further significantly improved by reducing the thickness in nanoscale. Extremely high efficient bulk photovoltaic effect is predicted in high quality ferroelectric ultrathin films. [ABSTRACT FROM AUTHOR]