A GaN bulk crystal with improved structural quality grown by the ammonothermal method

Abstract

The realization of high-performance optoelectronic devices, based on GaN and other nitride semiconductors, requires the existence of a high-quality substrate. Non-polar or semipolar substrates have recently been proven to provide superior optical devices to those on conventional c-plane substrates. Bulk GaN growth enables GaN substrates sliced along various favourable crystal orientations. Ammonothermal growth is an attractive method for bulk GaN growth owing to its potential to grow GaN ingots at low cost. Here we report on improvement in the structural quality of GaN grown by the ammonothermal method. The threading dislocation densities estimated by plan-view transmission electron microscopy observations were less than 1 x 10(6) cm(-2) for the Ga face and 1 x 10(7) cm(-2) for the N face. No dislocation generation at the interface was observed on the Ga face, although a few defects were generated at the interface on the N face. The improvement in the structural quality, together with the previous report on growth rate and scalability, demonstrates the commercial feasibility of the ammonothermal GaN growth.

KCa4(BO3)3:Ln3+ (Ln = Dy, Eu, Tb) phosphors for near UV excited white–light–emitting diodes

“…The crystal structure shows three different 11 B sites in KCa 4 (BO 3 ) 3 in a 1:1:1 ratio. To achieve the separation of these sites we therefore acquired a STMAS spectrum on KCa 4 (BO 3 ) 3 . The 2D STMAS spectra of KCa 4 (BO 3 ) 3 (Fig.…”

“…To achieve the separation of these sites we therefore acquired a STMAS spectrum on KCa 4 (BO 3 ) 3 . The 2D STMAS spectra of KCa 4 (BO 3 ) 3 (Fig. 3) show at least two well-resolved 11 B peaks (B1 and B2) on its isotropic (F1) dimension.…”

“…Being mercury-free, they are expected to be a viable replacement for conventional luminescent and fluorescent lamps in the near future. [1][2][3][4][5][6] One of the most fashionable approaches to produce white light is uniting a blue InGaN based LED with a broadband yellow-emitting Y 3 Al 5 O 12 :Ce 3+ (YAG) phosphor. However, this system lacks thermal stability at higher temperatures above 150 o C. Also, the resultant white light exhibits low color rendering index (R a ) due to lack of individual blue, red and green region colors.…”

“…Eventually 3 were mixed and ground well in an agate mortar to obtain a fine and homogeneous powder. The mixture was then annealed in a furnace in air atmosphere at 800 o C for 7 h in alumina boats and cooled to room temperatures.…”

Average and Local Structure, Debye Temperature, and Structural Rigidity in Some Oxide Compounds Related to Phosphor Hosts

“…1,2 PCLEDs generally contain two components, a blue or near-UV LED chip and a rare-earth substituted phosphor or phosphors that convert the LED emission to longer wavelengths, producing broad spectrum white light emission. The phosphor is a crucial component, impacting the overall luminous efficacy, color temperature, color rendition, and thermal stability of the resulting white light.…”