Depletion region

About: Depletion region is a research topic. Over the lifetime, 9393 publications have been published within this topic receiving 145633 citations.

Semiconductor‐Based Photoelectrochemical Water Splitting at the Limit of Very Wide Depletion Region

Abstract: In semiconductor-based photoelectrochemical (PEC) water splitting, carrier separation and delivery largely relies on the depletion region formed at the semiconductor/water interface. As a Schottky junction device, the trade-off between photon collection and minority carrier delivery remains a persistent obstacle for maximizing the performance of a water splitting photoelectrode. Here, it is demonstrated that the PEC water splitting efficiency for an n-SrTiO3 (n-STO) photoanode is improved very significantly despite its weak indirect band gap optical absorption (α 3 photoanodes are fabricated with their bulk heavily doped with oxygen vacancies but their surface lightly doped over a tunable depth of a few hundred nanometers, through a simple low temperature re-oxidation technique. The graded doping profile widens the depletion region to over 500 nm, thus leading to very efficient charge carrier separation and high quantum efficiency (>70%) for the weak indirect transition. As a result, this simultaneous optimization of the light absorption, minority carrier (hole) delivery, and majority carrier (electron) transport by means of a graded doping architecture may be useful for other indirect band gap photocatalysts that suffer from a similar problem of weak optical absorption.

Role of One-Dimensional Ribbonlike Nanostructures in Dye-Sensitized TiO2-Based Solar Cells

Abstract: In dye-sensitized solar cells, there is a competition between transport of electrons through the porous semiconductor electrode toward the conducting substrate and back-reaction of electrons to recombination with I-3(-) ions on the semiconductor electrolyte interface, which determines the charge collection efficiency and is strongly influenced by the electronic site distribution in intraband and geometrical structure of the semiconductors. Herein, we systematically analyze the electrochemical parameters of TiO2 nanoribbon- and nanoparticle-based electrodes by electrochemical impedance spectroscopy. The results show that the intrinsic one-dimensional crystalline structure of TiO2 nanoribbons can promote formation of a space charge layer on the surface of the semiconductor, which effectively blocks the recombination of electrons with I-3(-) ions in the semiconductor electrolyte interface, resulting in an increase of electron lifetime and a higher cell voltage. Furthermore, the boundaryless structure of the TiO2 nanoribbons provides efficient channels for electron transport and therefore increases electron diffusion length. The combination of TiO2 nanoparticle-based electrode with TiO2 nanoribbons can significantly improve energy conversion efficiency of similar to 60%. These data provide a basic understanding of the role of TiO2 geometrical structure in solar energy conversion.

Advantages of the graded-channel SOI FD MOSFET for application as a quasi-linear resistor

Abstract: In this paper, we analyze the previously unexpected advantages of asymmetric channel engineering on the MOS resistance behavior in quasi-linear operation, such as used in integrated continuous-time tunable filters. The study of the two major figures of merit in such applications as on-resistance and nonlinear harmonic distortion, is supported by both measurements and simulations of conventional and graded-channel (GC) fully depleted silicon-on-insulator (SOI) MOSFETs. The quasi-linear current-voltage characteristics of GC transistors show a decrease of the on-resistance as the length of the low doped region in the channel is increased, as well as an improvement in the third-order harmonic distortion (HD3), when compared with conventional transistors. A method for full comparison between conventional and GC SOI MOSFETs is presented, considering HD3 evolution with on-resistance tuning under low voltage of operation. Results demonstrate the significant advantages provided by the asymmetrical long channel transistors.

Planar semiconductor device having high breakdown voltage

Abstract: A planar semiconductor device having a high breakdown voltage includes a semiconductor layer of a first conductivity type and a first semiconductor region of a second conductivity type selectively formed, together with the semiconductor layer, in the surface of the semiconductor layer forming a pn junction. The first semiconductor region is formed to have an impurity concentration higher than that of the semiconductor layer and therefore a resistivity higher than that of the semiconductor layer. A second semiconductor region of the second conductivity type having an impurity concentration lower than that of the first semiconductor region, is formed around and in contact with the first semiconductor region and together with the semiconductor layer constitutes a pn junction. A high resistance film is formed at least over the first semiconductor region and the second semiconductor region. A voltage is applied across the high resistance film to create a uniform electric field in the high resistance film.