Engineering Strain in InGaN/GaN Multiple Quantum Wells for Improved Optical Devices

North Carolina State University, Raleigh NC

Investigators

Abstract

This grant is funded jointly by the Electronics, Photonics, and Magnetic Devices (EPMD) Program in the Division of Electrical, Communications and Cyber Systems (ECCS) and by the Electronic and Photonic Materials (EPM) Program in the Division of Materials Research (DMR). The proposed research addresses fundamental issues related to material growth and control of strain in Quantum-Wells through experimental and theoretical studies. The outcomes of this work include new material growth techniques and technology of optical devices that are vital for advancing the current state of the art LED technology. An enormous advantage is expected in the cost of solid state lighting by enabling device operation with higher injection current. Both graduate and undergraduate students will be involved in the research and will be trained in interdisciplinary areas. The proposed research is a unique opportunity for graduate and undergraduate students at to acquire interdisciplinary training and research experience in the field solid state lighting and optical displays. These students will be positioned to become the next generation leaders in advanced lighting technology. The project's goal is to integrate technical and scientific achievements through this requested funding with industries. Material growth approaches using Metal Organic Chemical Vapor Deposition (MOCVD) are proposed to allow control of the impact of strain on GaN based devices and improve the characteristics of Light Emitting Diodes (LEDs) such as quantum efficiency and droop. Strain balanced multiple quantum well (SBMQW) structures made of a thick InxGa1-xN template on which InyGa1-yN/GaN Multi-Quantum-Wells (MQWs) with x < y will be grown. They will consist of tensile-stressed GaN barriers and compressive-stressed InyGa1-yN wells. Different x, y values and well, barrier thicknesses will be explored to evaluate their impact on emission wavelength. Designs will be explored where the tensile and compressive stresses are balanced out allowing MQWs to match the lattice parameter of the InxGa1-xN substrate. The experimental studies will be supported by theoretical modeling of strain. A special MOVD reactor will be employed to reduce gas phase reactions and increase the InN composition. The growth rate and temperature will be suitably adjusted to optimize the thick InGaN substrates. Planar and side-wall LED structures will be explored to demonstrate the advantages of the proposed material strain studies and obtain longer emission wavelengths and better External Quantum Efficiency than conventional InGaN/GaN QW structures. The research will advance the basic understanding of the strain in InGaN/GaN Multi-Quantum-Wells through experimental and theoretical studies. It will allow to advance the current state of the art LED technology.