Group III-Nitride Based Electronic and Optoelectronic Integrated Circuits for Smart Lighting Applications
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Group III-Nitride Based Electronic and Optoelectronic Integrated Circuits for Smart Lighting Applications J. Justice, A. Kadiyala, J. Dawson and D. Korakakis Lane Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown, WV 26506 U.S.A. ABSTRACT With general lighting applications being responsible for over 20% of the energy consumption in the United States, advances in solid-state lighting have the potential for considerable energy and cost savings. The United States Department of Energy predicts that the increased use of solid state lighting will result in a 46% lighting consumption energy savings by the year 2030. Smart lighting systems have the potential for reducing energy costs while also providing a means for short distance data transmission via free space optics. The group IIInitride (III-N) family of materials, including aluminum nitride (AlN), gallium nitride (GaN), indium nitride (InN), their binary and ternary alloys, are uniquely situated to provide light emitting diodes (LEDs) across the full visible spectrum, photodetectors (PDs) and high power, high speed transistors. In this work, aluminum gallium nitride (AlGaN) / GaN high electron mobility transistors (HEMTs) and indium gallium nitride (InGaN) photodiodes (PDs) are fabricated and characterized. HEMTs and LEDs (or PDs) are grown on the same substrate for the purpose of creating electronic and optoelectronic integrated circuits. INTRODUCTION Since the successful fabrication of the first blue III-N based light emitting diodes (LEDs) by Shuji Nakamura et al. [1], GaN LEDs have become ubiquitous in the solid-state lighting industry, making up more than 90% of the market share for white light LEDs [2]. In recent years, III-N based high electron mobility transistors (HEMTs) have found a niche market for highpower, high-speed electronics applications [3]. Smart lighting techniques, such as free space optic (FSO) systems have also begun to be integrated into general lighting for short distance, line-of-sight communication [4-5]. This application is especially attractive for secure communication within an office building, for example. To date, current FSO systems usually employ a solid-state lighting device that is pulse width modulated using silicon logic circuits on separate chips. The light turns on and off so fast, it is not noticed by the human eye, but can be detected by photodiodes. In this work, the authors propose to use GaN HEMTs on the same chip as LEDs and PDs to drive the emitters and amplify the detectors respectively. GaN LEDs have previously been reported [6-7], and are not the focus of this article. Instead, HEMTs and PDs are fabricated and characterized. In addition, a method for growing and fabricating HEMTs and LEDs on the same substrate is discussed. EXPERIMENT For this work, group III-nitride based LEDs, PDs, and HEMTs were fabricated separately on insulating GaN epilayers. The GaN epilayers were grown in an Aixtron 200/4 RF-S MOVPE
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system on AlN buffer layers on sapphire substrates. Trimeth
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