Growth, fabrication and physical properties of nitride quantum dot based optical devices: light emitting diodes, laser diodes and photodetectors

Lead Research Organisation: University of Sheffield
Department Name: Electronic and Electrical Engineering

Abstract

GaN-based optoelectronic devices have been a topic of intense research due to the wide range of applications, including short wavelength laser diodes for next generation digital versatile disk (DVD), blue/green light emitting diodes for large scale full-color displays and solid state lighting as, ultraviolet light emitting diodes for biology, chemistry and environmental protection and photodetectors for fame and heat sensors monitor. For example, the storage capacity of GaN-based DVD is about four time higher than that of currently used GaAs-DVD. The popularly used incandescent lamp can be replaced by GaN-based solidstate lighting, which can greatly save energy and have a much longer life-time. However, due to the limits of the current technology, it is becoming more difficult to continuously improve the performance of the existing GaN-based optoelectronics. Therefore, it is very interesting to develop low dimensional GaN-based optoelectronics, such as GaN quantum dot based optoelectronic since improved performance is theoretically expected.The proposed programme undertakes a study of the formation, structure and optical properties of nitride quantum dots, and their application to optoelectroic devices: light emitting diodes, laser diodes and photodetectors in the region from ultraviolet to blue. The programme will be carried out in Department of Electronic and Electrical Engineering, the University of Sheffield and will develop state-of-the-art technologies for fabrication of above mentioned GaN-based devices with highly improved performance.

Publications

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Wang Q (2008) Influence of annealing temperature on optical properties of InGaN quantum dot based light emitting diodes in Applied Physics Letters

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Wang Q (2008) Growth and optical investigation of self-assembled InGaN quantum dots on a GaN surface using a high temperature AlN buffer in Journal of Applied Physics

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Wang Q (2009) MOCVD growth and optical study of InGaN quantum dots and their emitters on a high quality GaN layer grown using a high temperature AlN as buffer in physica status solidi c

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Wang Q (2007) The influence of a capping layer on optical properties of self-assembled InGaN quantum dots in Journal of Applied Physics

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Trager-Cowan C (2008) Electron Channeling and Ion Channeling Contrast Imaging of Dislocations in Nitride Thin Films in Microscopy and Microanalysis

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Thomson J (2006) The influence of acceptor anneal temperature on the performance of InGaN/GaN quantum well light-emitting diodes in Journal of Applied Physics

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Davies S (2009) Optical and microstructural studies of InGaN/GaN quantum dot ensembles in Applied Physics Letters

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Davies S (2010) Influence of the GaN barrier thickness on the optical properties of InGaN/GaN multilayer quantum dot heterostructures in Applied Physics Letters

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Davies S (2009) Influence of crystal quality of underlying GaN buffer on the formation and optical properties of InGaN/GaN quantum dots in Applied Physics Letters

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Davies S (2009) Optical spectroscopy of InGaN-GaN quantum dot ensembles in physica status solidi c

 
Description o Growth of InGaN QDs has been well established, and thus an ultra-high InGaN QD density of up to 10^11/cm^2 has been achieved, which is extremely important for growth of InGaN QD based optical devices. Those results reported are best so far.
o The formation mechanism of InGaN QDs has been investigated, showing that the lattice-mismatch is not only the driving force. The growth parameters such as NH3 flow-rate can certainly change the growth mode, which is massively different from the convention III-V QDs. The structural investigation by using high resolution transmission electron microscope has been carried out to identify the best QDs for growth of device materials
o It is first time to find that the crystal quality of the GaN underneath is extremely important for achieving ultra-high InGaN QD density. Currently, huge efforts have been put on the optimization of growth conditions for InGaN QDs themselves world-wide, which may not be a right way to go. We believe that it is why the reports published in the area of InGaN based QDs so far are less impressive. Our results give a best way forward.
o The optical properties have been extensively investigated (see publication 1, 2, 4, 5, 7, and 8). Most importantly, a stimulated emission at room temperature with a low threshold has been observed.
o Device fabrication of InGaN QD emitters has been well established. Unlike the standard InGaN quantum well based emitters, the conditions for device fabrication had to be carefully optimized in order to avoid any damage due to thermal annealing for p-type activation, as the growth temperature of InGaN QDs is lower than that for a standard InGaN quantum well. InGaN QD-based LEDs with high performance has been reported.
Exploitation Route joint publication and joint grant applications and significantly support the university spin-out
Sectors Education,Electronics,Energy,Environment,Healthcare
 
Description The growth technologies developed through the project has been widely used for other projects via III-V centre, and thus widely benefits the III-nitride community in the UK. The relevant growth technologies developed have significantly benefited the university spin-out. The Ph.D student, funded through the project, was awarded "Year 2009 Chinese Government Award for Outstanding Chinese Students Abroad" in recognition of his excellent Ph.D work. The award includes a certificate and a cas
Sector Education,Electronics,Energy,Environment,Healthcare
Impact Types Cultural,Economic
 
Title Using a thin protective layer under a mask when etching a nano-rod LED 
Description A light emitting diode 201 comprising device layers 210, 215, 220 (fig 2a) on semiconductor wafer substrate 205 has a protective layer 225 preferably comprising indium-tin oxide, zinc oxide or titanium oxide that may be less than 50nm and more preferably 20nm thick. This layer protects subsequent processing steps which may include forming a mask layer or layers 230, 235 removing the mask layer, or etching filling materials provided over the selectively etched semiconductor wafer. The mask may comprise a first silicon dioxide or nitride layer 230 and a metal llayer 253, such as nickel that is annealed on the first layer. The device layers are preferable etched to form nano-scale nano-rods or nano-pillars 202 which may be treated ( cured ) with hot nitric acid on surface 202a before a filling layer is applied (240 fig 3) and then etched back to allow a contact layer (245) and pads (250, 255) to be formed. 
IP Reference GB2487917 
Protection Patent application published
Year Protection Granted 2012
Licensed Yes
Impact contribute to the funds-raise of the spinout