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Growth Of N-type AlGaN With High Aluminum Content For Solar-blind UV Detector Use

Posted on:2012-09-07Degree:MasterType:Thesis
Country:ChinaCandidate:C LiuFull Text:PDF
GTID:2218330362956675Subject:Physical Electronics
Abstract/Summary:PDF Full Text Request
By means of tunable [TMA/(TMa+TMG)] flux ratio, the highly conductive n-type (Al)GaN epilayers with various Aluminum content were successfully grown on high quality AlN Template or AlN/AlGaN Supperlattices using metal organic chemical vapor deposition (MOCVD). The surface morphography, crystal quality, optical property and the electrical performance of these n-(Al)GaN films were characterized by Microscopy, Atom Force Microscopy (AFM), X-ray diffraction (XRD), Transmission Spectra, Raman Spectra, Hall measurement, Capacitance-Voltage characterization.Experiment results indicate that high Al-content AlxGa1-xN (x>0.4) is available by decreasing the flow of TEG while maintaining that of TMA as constant. However, due to lower migration property of Al atom compared to Ga atom, the decreasing flow of TEG results in the deterioration of the surface morphography of AlGaN film with increasing Al content.N-type (Al)GaN epilayers can be obtained by introducing silane as a dopant. The increasing of molar flow of silane has a positive influence on the carrier density of the epilayers. But there is an optimized amount of silane corresponding to the highest mobility, in another word, the mobility of n-type film would first increase and then decrease when adding more silane. Moreover, the aggrandizement of Si atom in AlGaN film will induce a demolishment of crystal lattice and reduce the size of the lattice as well.Specially, when it comes to n-AlGaN, the Si dopant level deepens along with the increase of Al content. Thus the carrier density declines with the Al content's increase when the flow of silane remains constant. Meanwhile, since the lattice constant decrease with higher Al content, the opportunity of occurrences of scattering between electron and crystal lattice is greatly increased, and the mobility of the film drops as a result.Finally, the data of early-stage research into the In-Si co-doping suggests that the introduction of Indium into the AlGaN material system can slightly improve the crystal quality and surface morphography of the AlGaN film.As a whole, the high Al content n-AlGaN is quite suitable for the device fabrication of solar-blind ultraviolet photodetector. And the analysis of n-doping characteristics of AlGaN can facilitate further experiment on growth of III-Nitride films.
Keywords/Search Tags:Metal Organic Chemical Vapor Deposition (MOCVD), AlGaN, N-type Doping, In-Si Co-doping, Ultraviolet Photodetector
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