Ultrafast, superhigh gain visible-blind UV detector and optical logic gates based on nonpolar a-axial GaN nanowire

Abstract

Nonpolar a-axial GaN nanowire (NW) was first used to construct the MSM (metal-semiconductor-metal) symmetrical Schottky contact device for application as visible-blind ultraviolet (UV) detector. Without any surface or composition modifications, the fabricated device demonstrated a superior performance through a combination of its high sensitivity (up to 10(4) A W(-1)) and EQE value (up to 10(5)), as well as ultrafast (<26 ms) response speed, which indicates that a balance between the photocurrent gain and the response speed has been achieved. Based on its excellent photoresponse performance, an optical logic AND gate and OR gate have been demonstrated for performing photo-electronic coupled logic devices by further integrating the fabricated GaN NW detectors, which logically convert optical signals to electrical signals in real time. These results indicate the possibility of using a nonpolar a-axial GaN NW not only as a high performance UV detector, but also as a stable optical logic device, both in light-wave communications and for future memory storage.

Enhanced UV detection by non-polar epitaxial GaN films

“…Polar c-axis GaN epilayers possess nonpolar m-or a-plane side surfaces while nonpolar a-axis oriented GaN has polar and semipolar sidewalls. 21 Absence of spontaneous polarization in the nonpolar direction results in weaker separation of electron and hole wavefunctions and in efficient recombination of the charge carriers leading to lesser photocurrent. 22 Since the transport of the carriers occurs perpendicular to the growth direction, 23 for the polar c-GaN epilayer, nonpolar sidewalls resulted in lesser photocurrents and hence lower responsivity while in the case of nonpolar a-GaN epilayer with polar and semipolar sidewalls, polarization effect resulted in inefficient recombination and higher photocurrents.…”

Ultraviolet Sensors Based on Two-Dimensional Zinc Oxide Structures

“…This makes ZnO, a potential candidate, as a UV sensor, and it is favourable over several materials for this application, such as gallium nitride [63] and silicon carbide [64]. ZnO has a large exciton binding energy (60 meV) compared with gallium nitride (26 meV), which makes it more suitable for optoelectronic applications, especially at temperatures near and above room temperature [27].…”

Low noise ultraviolet photodetector with over 100% enhanced lifetime based on polyfluorene copolymer and ZnO nanoparticles

“…Ultraviolet (UV) light detection technology has attracted significant attention due to its numerous applications for fire and smoke detection, missile warning, biological sensing, and so on . So far, typical UV detectors have been based on wide bandgap inorganic semiconductors such GaN, SiC, ZnO, and TiO 2 . However, the fabrication of photodetectors based on such materials is complicated and expensive, so further inorganic UV photodetectors development is hindered.…”