GaN thick films, grown on specially patterned 2" sapphire substrates by HVPE methods have lower b... more GaN thick films, grown on specially patterned 2" sapphire substrates by HVPE methods have lower bowing and are less susceptible to fracture then ones, grown on unpatterned substrates under the same growth conditions. Numerical calculation shows good agreement with experiments. Such substrates could be an alternative to expen-sive GaN wafers sliced from GaN boules.
GaN thick films, grown on specially patterned 2" sapphire substrates by HVPE methods have lo... more GaN thick films, grown on specially patterned 2" sapphire substrates by HVPE methods have lower bowing and are less susceptible to fracture then ones, grown on unpatterned substrates under the same growth conditions. Numerical calculation shows good agreement with experiments. Such substrates could be an alternative to expensive GaN wafers sliced from GaN boules.
The effect of growth parameters on stress in thick GaN films grown on sapphire by HVPE method was... more The effect of growth parameters on stress in thick GaN films grown on sapphire by HVPE method was investigated. We have found two modes of growth with different growth stress. Films grown in one mode have rough surfaces and low stress. The second mode leads to smooth surfaces but the films contain many cracks due to high growth stress. A combination of these modes allows growth of films without cracks and with smooth surfaces.
GaN films with thicknesses up to 3 mm were grown in two custom-made halide vapor phase epitaxy (H... more GaN films with thicknesses up to 3 mm were grown in two custom-made halide vapor phase epitaxy (HVPE) reactors. V-shaped defects (pits) with densities from 1 cm^-2 to 100 cm^-2 were found on the surfaces of the films. Origins of pit formation and the process of pit overgrowth were studied by analyzing the kinematics of pit evolution. Two mechanisms of pit overgrowth were observed. Pits can be overgrown intentionally by varying growth parameters to increase the growth rate of pit facets. Pits can overgrow spontaneously if a fast-growing facet nucleates at their bottom under constant growth conditions.
A free-standing bulk gallium nitride layer with a thickness of 365 μm and a diameter of 50 mm was... more A free-standing bulk gallium nitride layer with a thickness of 365 μm and a diameter of 50 mm was obtained by hydride vapor phase epitaxy on a sapphire substrate with a carbon buffer layer. The carbon buffer layer was deposited by thermal decomposition of methane in situ in the same process with the growth of a bulk GaN layer. The bulk GaN layer grown on the carbon buffer layer self-separated from the sapphire substrate during the cooling after the growth. The dislocation density was 8·10^6 cm^-2. The (0002) X-Ray rocking curve full width at half maximum was 164 arcsec.
The chemical resistance of quartz, aluminum oxide, boron nitride, molybdenum, and platinum in the... more The chemical resistance of quartz, aluminum oxide, boron nitride, molybdenum, and platinum in the environment of the hydride vapor phase epitaxy of gallium nitride was estimated by chemical equilibrium calculation. The interaction of materials with hydrogen, hydrogen chloride, chlorine, ammonia, and gallium chlorides was analyzed. The conditions in which the use of each material is permissible were determined.
La presente invention concerne deux variations de procedes de separation d'une couche superfi... more La presente invention concerne deux variations de procedes de separation d'une couche superficielle de cristal semi-conducteur. Dans la premiere variation du procede, un faisceau laser concentre est dirige sur le cristal de maniere telle que le foyer soit positionne dans le plan de separation de couche perpendiculaire a l'axe dudit faisceau, le faisceau laser est deplace en balayant le plan de separation de couche avec le foyer dans la direction depuis la surface cote ouvert du cristal en profondeur dans le cristal en formant une fente continue dont la largeur est augmentee a chaque passe du faisceau laser, l'operation precedente est realisee jusqu'a la separation de la couche superficielle. Dans la seconde variation du procede, une emission laser a impulsions est generee ; un faisceau laser concentre est dirige sur le cristal de maniere telle que le foyer soit positionne dans le plan de separation de couche perpendiculaire a l'axe dudit faisceau, un faisceau las...
The present invention proposes a light-emitting semiconductor device (300) comprising: a substrat... more The present invention proposes a light-emitting semiconductor device (300) comprising: a substrate (301), a first layer from n-type semiconductor (201) formed on the substrate (301), a second layer from p-type semiconductor (203); an active layer (202) arranged between the first and second layers (201, 203); a conductive layer (204) arranged on the second layer (203), a first contact (302) applied on the substrate (301), a second contact (303) applied on the conductive layer (204), wherein the substrate (301) comprises at least one through hole made in the form of truncated inverted pyramid, wherein the first, second, active and conductive layers (201, 203, 202, 204) are applied both on the horizontal areas of the substrate (301), and on the internal faces of the holes. Using of the truncated pyramids leads to relatively large coefficients of conversion of electrical energy to light, and light extraction.
We report results of calculations of radiative efficiency of In Ga N quantum wells embedded in wu... more We report results of calculations of radiative efficiency of In Ga N quantum wells embedded in wurtzite GaN x 1yx epilayer. It was found that misfit dislocations with density up to ; 10 5-6 cm y1 could improve the quantum efficiency of the In Ga N wells by more than 10 times because they reduce the quantum well built-in electric field. At higher densities, the x 1yx
Gallium Nitride substrates are crucial for the production of reliable GaN-based devices with high... more Gallium Nitride substrates are crucial for the production of reliable GaN-based devices with high current density: light emitting diodes and lasers, high-voltage diodes and transistors, and microwave high electron mobility transistors. However, the widespread use of GaN substrates is currently limited by their high price. To solve this problem, the Laser Slicing™process has been developed [1]: a method for lifting off a thin GaN film from the bulk GaN substrate. The demonstrated Laser Slicing™process does not require any special release layers and can be used both for lifting off pure GaN films and for lifting off GaN films with device structure. The application of such a process allows to reuse the expensive bulk GaN substrate many times and thereby reduce the cost of the devices. The proposed method is based on the effect of GaN decomposition caused by an ultrashort laser pulse focused inside a bulk GaN material. A femtosecond laser is focused inside bulk GaN, several microns und...
GaN thick films, grown on specially patterned 2" sapphire substrates by HVPE methods have lower b... more GaN thick films, grown on specially patterned 2" sapphire substrates by HVPE methods have lower bowing and are less susceptible to fracture then ones, grown on unpatterned substrates under the same growth conditions. Numerical calculation shows good agreement with experiments. Such substrates could be an alternative to expen-sive GaN wafers sliced from GaN boules.
GaN thick films, grown on specially patterned 2" sapphire substrates by HVPE methods have lo... more GaN thick films, grown on specially patterned 2" sapphire substrates by HVPE methods have lower bowing and are less susceptible to fracture then ones, grown on unpatterned substrates under the same growth conditions. Numerical calculation shows good agreement with experiments. Such substrates could be an alternative to expensive GaN wafers sliced from GaN boules.
The effect of growth parameters on stress in thick GaN films grown on sapphire by HVPE method was... more The effect of growth parameters on stress in thick GaN films grown on sapphire by HVPE method was investigated. We have found two modes of growth with different growth stress. Films grown in one mode have rough surfaces and low stress. The second mode leads to smooth surfaces but the films contain many cracks due to high growth stress. A combination of these modes allows growth of films without cracks and with smooth surfaces.
GaN films with thicknesses up to 3 mm were grown in two custom-made halide vapor phase epitaxy (H... more GaN films with thicknesses up to 3 mm were grown in two custom-made halide vapor phase epitaxy (HVPE) reactors. V-shaped defects (pits) with densities from 1 cm^-2 to 100 cm^-2 were found on the surfaces of the films. Origins of pit formation and the process of pit overgrowth were studied by analyzing the kinematics of pit evolution. Two mechanisms of pit overgrowth were observed. Pits can be overgrown intentionally by varying growth parameters to increase the growth rate of pit facets. Pits can overgrow spontaneously if a fast-growing facet nucleates at their bottom under constant growth conditions.
A free-standing bulk gallium nitride layer with a thickness of 365 μm and a diameter of 50 mm was... more A free-standing bulk gallium nitride layer with a thickness of 365 μm and a diameter of 50 mm was obtained by hydride vapor phase epitaxy on a sapphire substrate with a carbon buffer layer. The carbon buffer layer was deposited by thermal decomposition of methane in situ in the same process with the growth of a bulk GaN layer. The bulk GaN layer grown on the carbon buffer layer self-separated from the sapphire substrate during the cooling after the growth. The dislocation density was 8·10^6 cm^-2. The (0002) X-Ray rocking curve full width at half maximum was 164 arcsec.
The chemical resistance of quartz, aluminum oxide, boron nitride, molybdenum, and platinum in the... more The chemical resistance of quartz, aluminum oxide, boron nitride, molybdenum, and platinum in the environment of the hydride vapor phase epitaxy of gallium nitride was estimated by chemical equilibrium calculation. The interaction of materials with hydrogen, hydrogen chloride, chlorine, ammonia, and gallium chlorides was analyzed. The conditions in which the use of each material is permissible were determined.
La presente invention concerne deux variations de procedes de separation d'une couche superfi... more La presente invention concerne deux variations de procedes de separation d'une couche superficielle de cristal semi-conducteur. Dans la premiere variation du procede, un faisceau laser concentre est dirige sur le cristal de maniere telle que le foyer soit positionne dans le plan de separation de couche perpendiculaire a l'axe dudit faisceau, le faisceau laser est deplace en balayant le plan de separation de couche avec le foyer dans la direction depuis la surface cote ouvert du cristal en profondeur dans le cristal en formant une fente continue dont la largeur est augmentee a chaque passe du faisceau laser, l'operation precedente est realisee jusqu'a la separation de la couche superficielle. Dans la seconde variation du procede, une emission laser a impulsions est generee ; un faisceau laser concentre est dirige sur le cristal de maniere telle que le foyer soit positionne dans le plan de separation de couche perpendiculaire a l'axe dudit faisceau, un faisceau las...
The present invention proposes a light-emitting semiconductor device (300) comprising: a substrat... more The present invention proposes a light-emitting semiconductor device (300) comprising: a substrate (301), a first layer from n-type semiconductor (201) formed on the substrate (301), a second layer from p-type semiconductor (203); an active layer (202) arranged between the first and second layers (201, 203); a conductive layer (204) arranged on the second layer (203), a first contact (302) applied on the substrate (301), a second contact (303) applied on the conductive layer (204), wherein the substrate (301) comprises at least one through hole made in the form of truncated inverted pyramid, wherein the first, second, active and conductive layers (201, 203, 202, 204) are applied both on the horizontal areas of the substrate (301), and on the internal faces of the holes. Using of the truncated pyramids leads to relatively large coefficients of conversion of electrical energy to light, and light extraction.
We report results of calculations of radiative efficiency of In Ga N quantum wells embedded in wu... more We report results of calculations of radiative efficiency of In Ga N quantum wells embedded in wurtzite GaN x 1yx epilayer. It was found that misfit dislocations with density up to ; 10 5-6 cm y1 could improve the quantum efficiency of the In Ga N wells by more than 10 times because they reduce the quantum well built-in electric field. At higher densities, the x 1yx
Gallium Nitride substrates are crucial for the production of reliable GaN-based devices with high... more Gallium Nitride substrates are crucial for the production of reliable GaN-based devices with high current density: light emitting diodes and lasers, high-voltage diodes and transistors, and microwave high electron mobility transistors. However, the widespread use of GaN substrates is currently limited by their high price. To solve this problem, the Laser Slicing™process has been developed [1]: a method for lifting off a thin GaN film from the bulk GaN substrate. The demonstrated Laser Slicing™process does not require any special release layers and can be used both for lifting off pure GaN films and for lifting off GaN films with device structure. The application of such a process allows to reuse the expensive bulk GaN substrate many times and thereby reduce the cost of the devices. The proposed method is based on the effect of GaN decomposition caused by an ultrashort laser pulse focused inside a bulk GaN material. A femtosecond laser is focused inside bulk GaN, several microns und...
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