Developments of GaN Bulk Substrates for GaN Based LEDs and LDs
In the present work, we discuss the importance of bulk GaN substrates for GaN based LEDs and LDs. As crystal growth methods for growing bulk GaN, we study the hydride vapor phase epitaxial (HVPE) method and the pressure-controlled solution growth (PC-SG) method. The recent results obtained by these two methods are presented. The maximum size of the grown single crystals was 3 × 4 cm2 for the HVPE method and 12 mm diameter for the PC-SG method. Both methods can provide high quality GaN substrates, with a low dislocation density of the level of less than 106 cm–2.
GaN epitaxial growth on neodium gallate substrates
We have investigated the feasibility of neodium gallate (NdGaO3, NGO) as substrates for GaN epitaxial growth for the first time. GaN films deposited on neodium gallate substrates by the hydride vapor phase epitaxy technique have been found to be single-crystalline with the epitaxial relationship of GaN(0001)|NGO(011) and GaN[1010]|NGO[100], where the lattice mismatch between the film and the substrate is less than 2%. Photoluminescence (PL) of GaNNGO films at room temperature showed a strong band edge emission with little emission in the longer wavelength region. The carrier concentration and the electronmobility of GaNNGO films were 7 × 1019 cm−3 and 45 cm2/Vs, respectively. These results are superior to those of GaN/sapphire films deposited simultaneously under the same conditions.
Handbook of Concrete Engineering
Handbook of concrete engineering , Handbook of concrete engineering , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی