Date of Award

1-1-2011

Document Type

Campus Access Thesis

Department

Electrical Engineering

First Advisor

Asif Khan

Abstract

Deep ultraviolet (DUV) light emitting diodes (LEDs) based on group III-Nitrides have numerous potential applications in water and air purification, food sterilization, ultraviolet curing, chemical and biological sensors, and medical instrumentation. However, DUV LEDs, with peak emission wavelength between 250 and 320 nm, are prone to self-heating. This rise in temperature during normal operation leads to early saturation of the light output power of these devices at relatively low injection currents and degrades their external quantum efficiency. Furthermore, this high heat dissipation also decreases the reliability of these devices and shorten their life span. Consequently, thermal management of high power LEDs is a crucial area of research and development. Thermal impedance is one of the primary parameters characterizing the thermal properties of an LED. Thermal impedance quantifies the rise in the junction temperature of a device per unit of power dissipated. Lower thermal impedance of a device will result in higher dissipation of the heat energy and lower junction temperatures. In this thesis, the junction temperature and thermal impedance of square-geometry and micro-pixel AlGaN/AlGaN DUV LEDs are measured using the electroluminescence (EL) peak position shift and forward voltage shift methods. The EL peak-shift method was found to be more reliable than voltage-shift method to predict the thermal impedance for unpackaged devices. On the other hand, for packaged devices, the measurements using voltage-shift method were found to be more accurate than those from peak-shift method.

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