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Influence of dopants on defect formation in GaN

Description: Influence of p-dopants (Mg and Be) on the structure of GaN has been studied using Transmission Electron Microscopy (TEM). Bulk GaN:Mg and GaN:Be crystals grown by a high pressure and high temperature process and GaN:Mg grown by metal-organic chemical-vapor deposition (MOCVD) have been studied. Structural dependence on growth polarity was observed in the bulk crystals. Spontaneous ordering in bulk GaN:Mg on c-plane (formation of Mg-rich planar defects with characteristics of inversion domains) was observed for growth in the N to Ga polar direction (N polarity). On the opposite site of the crystal (growth in the Ga to N polar direction) Mg-rich pyramidal defects empty inside (pinholes) were observed. Both these defects were also observed in MOCVD grown crystals. Pyramidal defects were also observed in the bulk GaN:Be crystals.
Date: October 15, 2001
Creator: Liliental-Weber, Z.; Jasinski, J.; Benamara, M.; Grzegory, I.; Porowski, S.; Lampert, D.J.H. et al.
Partner: UNT Libraries Government Documents Department

Influence of Mg and In on defect formation in GaN; bulk and MOCVD grown samples

Description: Transmission electron microscopy studies were applied to study GaN crystals doped with Mg. Both: bulk GaN:Mg crystals grown by a high pressure and high temperature process and those grown by metal-organic chemical-vapor deposition (MOCVD) have been studied. Structural dependence on growth polarity was observed in the bulk crystals. Spontaneous ordering (formation of polytypoids) was observed for growth in the N to Ga polar direction (N polarity). On the opposite site of the crystal (growth in the Ga to N polar direction) Mg-rich pyramidal defects with base on the basal planes and with walls inclined about 45O to these planes, empty inside (pinholes) were observed. A high concentration of these pyramidal defects was also observed in the MOCVD grown crystals. For samples grown with Mg delta doping planar defects were also observed especially at the early stages of growth followed by formation of pyramidal defects. TEM and x-ray studies of InxGa{sub 1{minus}x}N crystals for the range of 28-45% nominal In concentration shows formation of two sub-layers: strained and relaxed, with a much lower In concentration in the strained layer. Layers with the highest In concentration were fully relaxed.
Date: November 22, 2000
Creator: Liliental-Weber, Z.; Benamara, M.; Jasinski, J.; Swider, W.; Washburn, J.; Grzegory, I. et al.
Partner: UNT Libraries Government Documents Department

Evolution of deep centers in GaN grown by hydride vapor phaseepitaxy

Description: Deep centers and dislocation densities in undoped n GaN, grown by hydride vapor phase epitaxy (HVPE), were characterized as a function of the layer thickness by deep level transient spectroscopy and transmission electron microscopy, respectively. As the layer thickness decreases, the variety and concentration of deep centers increase, in conjunction with the increase of dislocation density. Based on comparison with electron irradiation induced centers, some dominant centers in HVPE GaN are identified as possible point defects.
Date: April 18, 2001
Creator: Fang, Z.-Q.; Look, D.C.; Jasinski, J.; Benamara, M.; Liliental-Weber, Z. & Molnar, R.J.
Partner: UNT Libraries Government Documents Department