Abstract: A GaN single crystal is grown by synthesizing GaN in vapor phase, piling a GaN crystal on a substrate, producing a three-dimensional facet structure including facets in the GaN crystal without making a flat surface, maintaining the facet structure without burying the facet structure, and reducing dislocations in the growing GaN crystal. The facet structure reduces the EPD down to less than 106 cm−2.

Abstract: A freestanding GaN single crystal substrate is made by the steps of preparing a (111) GaAs single crystal substrate, forming a mask having periodically arranged windows on the (111) GaAs substrate, making thin GaN buffer layers on the GaAs substrate in the windows of the mask, growing a GaN epitaxial layer on the buffer layers and the mask by an HVPE or an MOC, eliminating the GaAs substrate and the mask away and obtaining a freestanding GaN single crystal substrate. The GaN single crystal has a diameter larger than 20 mm and a thickness more than 0.07 mm, being freestanding and substantially distortion-free.

Abstract: GaN-type LED or LD made on a (0001)GaN single crystal substrate having natural cleavage planes on sides. A GaN/GaN LED has a shape of a equilateral triangle, parallelogram, trapezoid, equilateral hexagon or rhombus. A GaN/GaN LD has a shape of a parallelogram with cleavage planes on two ends and two sides. Another GaN/GaN LD has a shape of a square with cleavage planes on two ends.

Abstract: The present invention provides an epitaxial wafer comprising a (111) substrate of a semiconductor having cubic crystal structure, a first GaN layer having a thickness of 60 nanometers or more, a second GaN layer having a thickness of 0.1 &mgr;m or more and a method for preparing it.

Abstract: GaN single crystal substrates are produced by slicing a GaN single crystal ingot in the planes parallel to the growing direction. Penetration dislocations which have been generated in the growing direction extend mainly in the bulk of the GaN substrate. A few of the threading dislocations appear on the surface of the GaN substrate. GaN substrates of low-dislocation density are obtained.

Abstract: An n-type GaN substrate having a safe n-type dopant instead of Si which is introduced by perilous silane gas. The safe n-dopant is oxygen. An oxygen doped n-type GaN free-standing crystal is made by forming a mask on a GaAs substrate, making apertures on the mask for revealing the undercoat GaAs, growing GaN films through the apertures of the mask epitaxially on the GaAs substrate from a material gas including oxygen, further growing the GaN film also upon the mask for covering the mask, eliminating the GaAs substrate and the mask, and isolating a freestanding GaN single crystal. The GaN is an n-type crystal having carriers in proportion to the oxygen concentration.

Abstract: The present invention provides an epitaxial wafer comprising a (111) substrate of a semiconductor having cubic crystal structure, a first GaN layer having a thickness of 60 nanometers or more, a second GaN layer having a thickness of 0.1 &mgr;m or more and a method for preparing it.

Abstract: An epitaxial wafer enabling epitaxial growth at a high temperature includes a compound semiconductor substrate containing As or P, and a covering layer including GaN; or InN; or AlN; or a nitride mixed-crystalline material containing Al, Ga, In and N. The covering layer covers at least a front surface and a back surface of the substrate. A method of preparing such an epitaxial wafer including steps of growing the covering layer at a growth temperature of at least 300.degree. C. and less than 800.degree. C. so as to cover at least the front and back surfaces of the substrate, and then annealing the substrate having the covering thereon layer at a temperature of at least 700.degree. C. and less than 1200.degree. C.

Abstract: A process for forming a high quality epitaxial compound semiconductor layer of indium gallium nitride In.sub.x Ga.sub.1-x N, (where 0<x<1) on a substrate. A first gas including indium trichloride (InCl.sub.3) and a second gas including ammonia (NH.sub.3) are introduced into a reaction chamber and heated at a first temperature. Indium nitride (InN) is grown epitaxially on the substrate by nitrogen (N.sub.2) carrier gas to form an InN buffer layer. Thereafter, a third gas including hydrogen chloride (H1) and gallium (Ga) is introduced with the first and second gases into a chamber heated at a second temperature higher than the first temperature and an epitaxial In.sub.x Ga.sub.1-x N layer is grown on the buffer layer by N.sub.2 gas. By using helium, instead of N.sub.2, as carrier gas, the In.sub.x Ga.sub.1-x N layer with more homogeneous quality is obtained. In addition, the InN buffer layer is allowed to be modified into a GaN buffer layer.

Abstract: A light emitting device having higher blue luminance is obtained. A gallium nitride compound layer is formed on a GaAs substrate, and thereafter the GaAs substrate is at least partially removed for forming the light emitting device. Due to the removal of the GaAs substrate, the quantity of light absorption is reduced as compared with the case of leaving the overall GaAs substrate. Thus, a light emitting device having high blue luminance is obtained.

Abstract: A light emitting device having higher blue luminance is obtained. A gallium nitride compound layer is formed on a GaAs substrate, and thereafter the GaAs substrate is at least partially removed for forming the light emitting device. Due to the removal of the GaAs substrate, the quantity of light absorption is reduced as compared with the case of leaving the overall GaAs substrate. Thus, a light emitting device having high blue luminance is obtained.