Growth Of Gallium Nitride Using Molecular Beam Epitaxy

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ISBN 13 :
Total Pages : 133 pages
Book Rating : 4.:/5 (78 download)

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Download or read book Molecular Beam Epitaxy (MBE) Growth of Rare Earth Doped Gallium Nitride for Laser Diode Application written by and published by . This book was released on 2006 with total page 133 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this dissertation is to demonstrate the visible laser emission from rare earth doped GaN grown on sapphire and silicon substrate. The research presented in this dissertation focused on exploration of RE's physics and laser characteristics and investigating site selective laser emission. In this study, the first visible (red) lasing emission from Eu-doped GaN thin films grown on sapphire substrates was demonstrated. The edge emission fulfills the requirements of stimulated emission properties: super-linear characteristic, spectrum line narrowing, polarization effect, lifetime reduction, and longitudinal modes in a Fabry-Perot cavity. The GaN:Eu active layer has low threshold (~10kW/cm2) for the onset of lasing. The optical gain and loss are of the order of 50 and 20cm-1, respectively. Growth conditions are investigated for gain enhancement and loss reduction. To obtain the high gain and low loss active layer, N-rich growth conditions are required. Channel waveguide cavities result in 5x increases in gain value compared to planar waveguides. To utilize the performance and flexibility of silicon microelectronics, we used silicon (111) substrate, which incorporated several AlGaN and AlN thin films as buffer, strain compensation and bottom optical cladding layers. With this substrate, we developed the laser structure emitting visible wavelength. We have utilized Eu-doped GaN for the active medium within a structure consisting of a top cladding AlGaN layers grown by MBE on a Si substrate. Stimulated emission (SE) was obtained at room temperature from Eu3+ at 620nm, with a threshold of ~117kW/cm2. Values of modal gain and loss of ~ 100 and 46 cm-1 were measured. This demonstration indicates that utilizing rare earths a range of lasers on Si can be obtained, covering the UV, visible and IR regions, thus enabling a significant expansion of optoelectronic and microelectronic integration. The dependence of optical modal gain and loss on GaN:Eu growth temperature is also conducted in this dissertation. The modal gain and loss in the GaN:Eu layer were a strong function of the optically active Eu atomic concentration and of the interface quality between the active layer and the top cladding layer, which in turn depended on the growth temperature. Optimum optical properties of maximum modal gain of ~ 100 cm-1 and minimum loss of ~ 46 cm-1 were obtained for growth at 800°C. We investigated site-specific Eu3+ stimulated emission in GaN:Eu laser structures. Two main Eu sites have been identified from emission peaks associated with the 5D0 to 7F2 transition during above band gap optical pumping with a pulsed N2 laser (337 nm): (a) Eux emitting at ~ 620 nm - present in short cavities (~100m), exhibiting stimulated (side) emission threshold and a fast decay time constant (30-35 s); (b) Euy emitting at ~ 621 nm - present in long cavities (~7mm) and in surface emission, exhibiting no stimulated emission threshold and a slow decay time constant (150-250 s).