Date of Award

Spring 2021

Document Type

Open Access Thesis

Department

Electrical Engineering

First Advisor

Ahmad Iftikhar

Abstract

III-Nitride based deep ultraviolet (DUV) light emitting diodes are non-toxic light sources that are highly desirable to replace current mercury lamp-based technology for air and water purification, surface and object disinfection, and sterilization. In the present. By freezing out defect related conduction pathways at temperatures less than 50K, the external quantum efficiency (EQE) of an interconnected array of 1,296 AlGaN DUV micropixels is improved by 4 times, underscoring the importance of defect management. Assuming a current injection efficiency (CIE) of 100% and considering that the light extraction efficiency (LEE) is constant with temperature, the 4-fold increase in the EL signal is attributed to the increase of the internal quantum efficiency (IQE). A thorough investigation of the current-voltage (I-V) characteristics revealed two distinct slopes with turn-on voltages of 2.7 V and 4.5 V. The low turn-on voltage path indicates the presence of defects in the bulk material and the higher turn-on voltage path is attributed to the multiple quantum well (MQW) active region. The turn-on voltage of 6.4 V at room temperature is larger than that expected from the active layer band gap of 4.3 eV and increases significantly with decreasing temperature. The contact resistances are likely responsible for the increased turn-on voltage with decreasing temperature. Remarkably, the series resistance of the device in high current regime that determined by highly resistive p-AlGaN layers of the structure, is nearly independent of temperature. This confirms polarization doping mechanism in these layers with reverse graded Al contents.

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