Abstract: In one instance, the invention provides a bulk crystal of group III nitride having a thickness of more than 1 mm without cracking above the sides of a seed crystal. This bulk group III nitride crystal is expressed as Gax1Aly1In1-x1-y1N (0?x1?1, 0?x1+y1?1) and the seed crystal is expressed as Gax2Aly2In1-x2-y2N (0?x2?1, 0?x2+y2?1). The bulk crystal of group III nitride can be grown in supercritical ammonia or a melt of group III metal using at least one seed crystal having basal planes of c-orientation and sidewalls of m-orientation. By exposing only c-planes and m-planes in this instance, cracks originating from the sides of the seed crystal are avoided.

Abstract: In one instance, the invention provides a group III nitride crystal having a first side exposing nitrogen polar c-plane of single crystalline or highly oriented polycrystalline group III nitride and a second side exposing group III polar surface, polycrystalline phase, or amorphous phase of group III nitride. Such structure is useful as a seed crystal for ammonothermal growth of bulk group III nitride crystals. The invention also discloses the method of fabricating such crystal. The invention also discloses the method of fabricating a bulk crystal of group III nitride by ammonothermal method using such crystal.

Abstract: Provided is a high-pressure reactor suitable for a high-pressure process using supercritical ammonia grow bulk crystal of group III nitride having lateral dimension larger than 2 inches or to form various transition metal nitrides. The reactor has nutrient distributed along the reactor's longitudinal axis and seed material positioned at the reactor's inner wall and along the reactor's longitudinal axis. Nutrient diffuses through supercritical ammonia from the reactor's longitudinal axis and deposits on the seed material positioned by the reactor's inner wall. Both the nutrient and seed material are heated by the same heater. Material growth can primarily be due to material diffusion through supercritical ammonia. This configuration and methodology reduce convective movement of supercritical ammonia due to temperature differential, providing a more quiescent environment in which group III nitride or transition metal nitride is formed.

Abstract: Group III nitride substrate having a first side of nonpolar or semipolar plane and a second side has more than one stripe of metal buried, wherein the stripes are perpendicular to group III nitride's c-axis. More than 90% of stacking faults exist over metal stripes. Second side may expose a nonpolar or semipolar plane. Also disclosed is a group III nitride substrate having a first side of nonpolar or semipolar plane and a second side with exposed nonpolar or semipolar plane. The substrate contains bundles of stacking faults with spacing larger than 1 mm. The invention also provides methods of fabricating the group III nitride substrates above.

Abstract: The present invention discloses an electronic device using a group III nitride substrate fabricated via the ammonothermal method. By utilizing the high-electron concentration of ammonothermally grown substrates having the dislocation density less than 105 cm?2, combined with a high-purity active layer of Ga1-x-yAlxInyN (0?x?1, 0?y?1) grown by a vapor phase method, the device can attain high level of breakdown voltage as well as low on-resistance. To realize a good matching between the ammonothermally grown substrate and the high-purity active layer, a transition layer is optionally introduced. The active layer is thicker than a depletion region created by a device structure in the active layer.

Abstract: In one instance, the invention provides a group III nitride crystal having a first side exposing nitrogen polar c-plane of single crystalline or highly oriented polycrystalline group III nitride and a second side exposing group III polar surface, polycrystalline phase, or amorphous phase of group III nitride. Such structure is useful as a seed crystal for ammonothermal growth of bulk group III nitride crystals. The invention also discloses the method of fabricating such crystal. The invention also discloses the method of fabricating a bulk crystal of group III nitride by ammonothermal method using such crystal.

Abstract: Group III nitride substrate having a first side of nonpolar or semipolar plane and a second side has more than one stripe of metal buried, wherein the stripes are perpendicular to group III nitride's c-axis. More than 90% of stacking faults exist over metal stripes. Second side may expose a nonpolar or semipolar plane. Also disclosed is a group III nitride substrate having a first side of nonpolar or semipolar plane and a second side with exposed nonpolar or semipolar plane. The substrate contains bundles of stacking faults with spacing larger than 1 mm. The invention also provides methods of fabricating the group III nitride substrates above.

Abstract: The present invention discloses a group III nitride wafer such as GaN, AlN, InN and their alloys having one surface visually distinguishable from the other surface. After slicing of the wafer from a bulk crystal of group III nitride with a mechanical method such as multiple wire saw, the wafer is chemically etched so that one surface of the wafer is visually distinguishable from the other surface. The present invention also discloses a method of producing such wafers.

Abstract: The present invention provides a method of growing an ingot of group III nitride. Group III nitride crystals such as GaN are grown by the ammonothermal method on both sides of a seed to form an ingot and the ingot is sliced into wafers. The wafer including the first-generation seed is sliced thicker than the other wafers so that the wafer including the first-generation seed does not break. The wafer including the first-generation seed crystal can be used as a seed for the next ammonothermal growth.

Abstract: The present invention discloses an electronic device using a group III nitride substrate fabricated via the ammonothermal method. By utilizing the high-electron concentration of ammonothermally grown substrates having the dislocation density less than 105 cm?2, combined with a high-purity active layer of Ga1-x-yAlxInyN (0?x?1, 0?y?1) grown by a vapor phase method, the device can attain high level of breakdown voltage as well as low on-resistance. To realize a good matching between the ammonothermally grown substrate and the high-purity active layer, a transition layer is optionally introduced. The active layer is thicker than a depletion region created by a device structure in the active layer.

Abstract: The present invention discloses an electronic device using a group III nitride substrate fabricated via the ammonothermal method. By utilizing the high-electron concentration of ammonothermally grown substrates having the dislocation density less than 105 cm?2, combined with a high-purity active layer of Ga1-x-yAlxInyN (0?x?1, 0?y?1) grown by a vapor phase method, the device can attain high level of breakdown voltage as well as low on-resistance. To realize a good matching between the ammonothermally grown substrate and the high-purity active layer, a transition layer is optionally introduced. The active layer is thicker than a depletion region created by a device structure in the active layer.

Abstract: The present invention discloses a new tool to slice crystal ingots by using laser beams. Ingot crystals of III-nitride such as GaN are immersed in alkali solutions and irradiated with scanned lines of laser beams to slice wafers out of the ingots. The method is expected to achieve approximately one order of magnitude smaller slicing loss with minimized slicing damage.

Abstract: The present invention in one preferred embodiment discloses a new design of HVPE reactor, which can grow gallium nitride for more than one day without interruption. To avoid clogging in the exhaust system, a second reactor chamber is added after a main reactor where GaN is produced. The second reactor chamber may be configured to enhance ammonium chloride formation, and the powder may be collected efficiently in it. To avoid ammonium chloride formation in the main reactor, the connection between the main reactor and the second reaction chamber can be maintained at elevated temperature. In addition, the second reactor chamber may have two or more exhaust lines. If one exhaust line becomes clogged with powder, the valve for an alternative exhaust line may open and the valve for the clogged line may be closed to avoid overpressuring the system. The quartz-made main reactor may have e.g. a pyrolytic boron nitride liner to collect polycrystalline gallium nitride efficiently.

Abstract: The present invention discloses a semi-insulating wafer of GaxAlyIn1-x-yN (0?x?1, 0?x+y?1) which is doped with bismuth (Bi). The semi-insulating wafer has the resistivity of 104 ohm-cm or more. Although it is very difficult to obtain a single crystal ingot of group III nitride, the ammonothermal method can grow highly-oriented poly or single crystal ingot of group III nitride having the density of dislocations/grain boundaries less than 105 cm?2. The invention also disclose the method of fabricating the semi-insulating group III nitride bulk crystals and wafers.

Abstract: The present invention discloses a novel composite substrate which solves the problem associated with the quality of substrate surface. The composite substrate has at least two layers comprising the first layer composed of GaxAlyIn1-x-yN (0?x?1, 0?x+y?1) and the second layer composed of metal oxide wherein the second layer can be removed with in-situ etching at elevated temperature. The metal oxide layer is designed to act as a protective layer of the first layer until the fabrication of devices. The metal oxide layer is designed so that it can be removed in a fabrication reactor of the devices through gas-phase etching by reactive gas such as ammonia.

Abstract: The present invention discloses an electronic device using a group III nitride substrate fabricated via the ammonothermal method. By utilizing the high-electron concentration of ammonothermally grown substrates having the dislocation density less than 105 cm?2, combined with a high-purity active layer of Ga1-x-yAlxInyN (0?x?1, 0?y?1) grown by a vapor phase method, the device can attain high level of breakdown voltage as well as low on-resistance. To realize a good matching between the ammonothermally grown substrate and the high-purity active layer, a transition layer is optionally introduced. The active layer is thicker than a depletion region created by a device structure in the active layer.

Abstract: The present invention discloses an electronic device using a group III nitride substrate fabricated via the ammonothermal method. By utilizing the high-electron concentration of ammonothermally grown substrates having the dislocation density less than 105 cm?2, combined with a high-purity active layer of Ga1-x-yAlxInyN (0?x?1, 0?y?1) grown by a vapor phase method, the device can attain high level of breakdown voltage as well as low on-resistance. To realize a good matching between the ammonothermally grown substrate and the high-purity active layer, a transition layer is optionally introduced. The active layer is thicker than a depletion region created by a device structure in the active layer.

Abstract: The present invention discloses a semi-insulating wafer of GaxAlyIn1-x-yN (0?x?1, 0?x+y?1) which is doped with bismuth (Bi). The semi-insulating wafer has the resistivity of 104 ohm-cm or more. Although it is very difficult to obtain a single crystal ingot of group III nitride, the ammonothermal method can grow highly-oriented poly or single crystal ingot of group III nitride having the density of dislocations/grain boundaries less than 105 cm?2. The invention also disclose the method of fabricating the semi-insulating group III nitride bulk crystals and wafers.

Abstract: The present invention discloses a novel composite substrate which solves the problem associated with the quality of substrate surface. The composite substrate has at least two layers comprising the first layer composed of GaxAlyIn1-x-yN (0?x?1, 0?x+y?1) and the second layer composed of metal oxide wherein the second layer can be removed with in-situ etching at elevated temperature. The metal oxide layer is designed to act as a protective layer of the first layer until the fabrication of devices. The metal oxide layer is designed so that it can be removed in a fabrication reactor of the devices through gas-phase etching by reactive gas such as ammonia.

Abstract: The present invention provides a method of growing an ingot of group III nitride. Group III nitride crystals such as GaN are grown by the ammonothermal method on both sides of a seed to form an ingot and the ingot is sliced into wafers. The wafer including the first-generation seed is sliced thicker than the other wafers so that the wafer including the first-generation seed does not break. The wafer including the first-generation seed crystal can be used as a seed for the next ammonothermal growth.