Two-step growth of high quality GaN using V/III ratio variation in the initial growth stage

MOVPE growth of GaAs on Ge substrates by inserting a thin low temperature buffer layer

“…Secondly it is necessary to grow a smooth buffer layer to obtain a good crystalline quality for device applications. Low temperature (LT) buffer layers have been successfully used for systems like InAs on GaAs [11], GaN on sapphire [12,13], GaAs on Si [14], and GaAs on Ge [15,16]. In this paper we report the improvement of the GaAs layer quality on Ge by inserting such an optimized LT-GaAs layer followed by a homoepitaxial grown high temperature (HT) GaAs layer.…”

Improvement of luminous intensity of InGaN light emitting diodes grown on hemispherical patterned sapphire

“…However, growth of high quality GaN film on patterned sapphire substrate is more difficult than that of conventional sapphire substrate (CSS). In order to improve the quality of GaN epitaxial layer, various growth techniques have been devised by adjusting growth parameters, such as III/V ratio, growth pressure, growth temperature, and annealing time [4,5].In this work, we proposed and investigated the metal organic chemical vapour deposition (MOCVD) growth of undoped GaN flims on a hemispherical patterned sapphire (HPS) substrate by controlling the V/III ratio during the initial growth stage. The fabricated white flash LEDs grown on HPS showed an improved luminous intensity and injection current due to both the reduction of the dislocation density and increase of the external efficiency compare to the samples grown on CSS.…”

“…In previous experiments using the CSS (0001), lower initial V/III ratio at HT-GaN growth was observed to improve the crystal quality of GaN layer. Several groups have demonstrated that the use of 3D-growth mode in the early stage of GaN growth plays an important role for the reduction of the threading dislocation density [4,5]. Improvement is attributed to the enhanced three-demensional growth mode, which result in rough surface morphology and larger island size in the initial stage of GaN growth.…”

Ultraviolet light emitting diodes

“…Gallium-rich regions at grain boundaries have been previously observed using cathodoluminescence and explained by a higher compressive strain (that is favourable for incorporation of Al) in the central area of the grains [91] and the larger lateral mobility of Ga adatoms on the growth surface and their accumulation at the grain boundaries [92]. To accommodate the relative difference in crystal orientation among the coalescing grains, the grain boundaries usually contain high density of extended defects [93]. As demonstrated in GaN [94], the extended defects, decorated with point defects, act as nonradiative recombination centres.…”