Laser-Patterned Blue-Green SiC LED
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0911-B10-01
Laser-Patterned Blue-Green SiC LED Sachin M Bet1,2, Nathaniel R Quick3, and Aravinda Kar1,2 1 Mechanical Materials and Aerospace Engineering (MMAE), University of Central Florida (UCF), Orlando, FL, 32816 2 Center for Research and Education in Optics and lasers (CREOL), College of Optics and Photonics (COP), UCF, Orlando, FL, 32816 3 AppliCote Associates, LLC, 1445 Dolgner Place, Suite 23, Sanford, FL, 32771 ABSTRACT The primary aim of this work is to fabricate silicon carbide (SiC) blue green light emitting diodes (LEDs) using novel laser doping technique. 6H:SiC (n-type) wafer samples and a Nd:YAG laser (1064nm wavelength) was used for fabrication of these LED’s. The doped structures were characterized for I-V characteristics, C-V characteristics and electroluminescence. Electroluminescence (EL) spectrum of the doped sample showed the output in the blue green (507.27nm) wavelength range, characterizing the p-n junction formed. INTRODUCTION Variety of semiconductors such as GaN (Gallium Nitride), GaP (Gallium Phosphide), AlGaAs (Aluminum Gallium Arsenide), InP (Indium Phosphide), Si (Silicon) and SiC are currently being studied for light emitting diode (LED) applications. Some of these materials are direct band gap semiconductor which is the preferred structure for LEDs, while other materials that have indirect band structure can operate as efficient LEDs based on different mechanisms. GaN, which is a direct bandgap semiconductor, operates in the blue to blue-green wavelength range with external quantum efficiencies of ~20%. However, the problem with the current LED technologies is that these devices are based on multilayer structures containing numerous interfaces. Such interfaces are weaker than the bulk material in terms of mechanical strength. Since the temperature of the device increases during its operation, two main reasons for the device failure or the degradation of device performance are: (i) thermal stresses at the interfaces causing delamination and stress-induced changes in the optical properties (e.g., refractive index) causing stress birefringence and depolarization loss, and (ii) interdiffusion of species across the interface altering the potential barrier height of each layer. Also the junction temperature adversely affects the performance of LEDs and laser diodes (LD), such as the laser wavelength, spectral width, and output power and diode reliability. The thermal conductivity of silicon carbide (SiC) is 400 – 500 W/m•K which is much higher than that of GaN (100 – 150 W/m•K). Also for applications of the diodes in space and harsh environments, SiC is better than GaN in terms of chemical and thermal stability, oxidation resistance, inertness to chemical attack, and radiation damage resistance. However, since SiC is an indirect bandgap semiconductor, it is much less efficient (~0.01%) than GaN based LEDs. Additionally, there is lack of extensive
research in the area of SiC based optoelectronic devices due to non-availability of single crystals of SiC of good quality (low defect densi
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