Poor Injection Efficiency Research Articles

Philosophy of Approaching a Laser Design Problem: Illustrated by the Design of Ultraviolet Vertical‐Cavity Laser Diodes

The objective of this article is to demonstrate a general approach to the problem of designing a novel laser diode. This involves first understanding prior work in this and related fields (literature survey), and then acquiring a thorough understanding of the relevant physics. This in turn enables the development and/or selection of appropriate models and tools for that problem followed by partitioning the problem into smaller solvable chunks. This involves identifying the key contributing factors affecting poor laser performance (sources of optical loss, poor injection efficiency, high thermal resistance, etc.), quantifying and ranking their relative importance, and finally finding solutions to these problems. The final step involves putting all these pieces back together to arrive at the final laser design. This step is challenging due to the strong coupling between electrical, optical, and thermal physics in a laser diode. Any design changes must be considered through all three lenses. Herein, this approach to laser design will be demonstrated in the context of a novel III–N‐based ultraviolet vertical‐cavity surface‐emitting laser diode (UV‐VCSEL).

Sensitization of TiO 2 and ZnO nanocrystalline films with acriflavine

A comparison of acriflavine sensitized photoelectrochemical cells based on nanocrystalline films of TiO 2 and ZnO shows that the short-circuit photocurrent of the latter system is nearly an order of magnitude larger, despite the poor injection efficiency from this dye to ZnO. The above observation and disparity in dark currents in the two systems indicate that recombination of the injected carrier with acceptors in the electrolyte is faster in the TiO 2 cell sensitized with the same dye. A study of 1/ f noise in the current through acriflavine and N3 dye coated nanocrystalline films of ZnO shows that that acriflavine is more strongly bonded to ZnO and not readily displaced by water molecules, which trap electrons and mediate recombination.

High-voltage silicon carbide rectifiers – results of experiments and simulation

Low reverse leakage silicon carbide pin rectifier diodes with a breakdown voltage reaching 1100 V are experimentally shown to have acceptably low forward voltage drops, dominated by the built-in voltage. Numerical simulations of the experimental structure, using a measured carrier lifetime of 25 ns, validate the existence of a conductive plasma in the lowly doped base layer, despite a poor injection efficiency, related to the incomplete ionization of the aluminium acceptor. Simulation also indicates the need for a lifetime of ~ 100 ns in a 3.0 kV device.