Communication—Electron-Beam Stimulated Release of Dislocations from Pinning Sites in GaN

To achieve low leakage in GaN-based power devices and improve reliability in optoelectronic devices such as laser diodes, it is necessary to reduce dislocation density in epitaxial layers and control their introduction during processing. We have previously shown that dislocations can be introduced at room temperature in GaN. The effect of electron-beam irradiation at fixed points on the shift of such freshly introduced dislocations in GaN is reported. Dislocations can be displaced up to 10-15 µm from the beam position. We conclude the main reason limiting the dislocation travelling distance is the existence of a high number of pinning sites.

Reference UVC LED Source

A compact reference UVC source based on commercially available LED has been developed. The article presents the design and results of the study of the optical characteristics of the radiation of the reference UVC LED source. The source provides a power density of radiation up to 400 μW/cm2 on area of 3×3 mm with inhomogeneity of 1.5 %.The emission band of a source with a maximum of 265 nm is predominantly 97 % in the UV-C spectrum region, and a small part of it is inUV-B and UV-A regions, 2.7 % and 0.3 %, respectively. The use of ComboSource for laser diodes allowed to precisionally stabilize the injection current and temperature of the LED. It is shown that overheating of the active region of the selected UV LED is only 10°C - 25°C at the recommended injection currents due to the peculiarities of its design. This results in a low degradation rate of the UV LED. Possible ways to improve the characteristics of the reference UVCsource are discussed.

DYNAMICAL AND TOPOLOGICAL INVARIANTS OF NONLINEAR DYNAMICS OF THE CHAOTIC LASER DIODES WITH AN ADDITIONAL OPTICAL INJECTION

Nonlinear chaotic dynamics of the of the chaotic laser diodes with an additional optical injection is computed within rate equations model, based on the a set of rate equations for the slave laser electric complex amplitude and carrier density. To calculate the system dynamics in a chaotic regime the known chaos theory and non-linear analysis methods such as a correlation integral algorithm, the Lyapunov’s exponents and Kolmogorov entropy analysis are used. There are listed the data of computing dynamical and topological invariants such as the correlation, embedding and Kaplan-Yorke dimensions, Lyapunov’s exponents, Kolmogorov entropy etc. New data on topological and dynamical invariants are computed and firstly presented.

Semipolar {202̅1} GaN Edge-Emitting Laser Diode on Epitaxial Lateral Overgrown Wing

Edge-emitting laser diodes (LDs) were fabricated on a reduced dislocation density epitaxial lateral overgrown (ELO) wing of a semipolar {202̅1} GaN substrate, termed an ELO wing LD. Two types of facet feasibility studies were conducted: (1) “handmade” facets, wherein lifted-off ELO wing LDs were cleaved manually, and (2) facets formed on wafers through reactive ion etching (RIE). Pulsed operation electrical and optical measurements confirmed the laser action in the RIE facet LDs with a threshold current of ~19 kAcm−2 and maximum light output power of 20 mW from a single uncoated facet. Handmade facet devices showed spontaneous, LED-like emission, confirming device layers remain intact after mechanical liftoff.