Sixpoint Materials, Inc.

Seoul Semiconductor Co., Ltd.

Edward Letts

Tadao Hashimoto

Masanori Ikari

Sierra Hoff

Daryl Key

In one instance, the seed crystal of this invention provides a nitrogen-polar c-plane surface of a GaN layer supported by a metallic plate. The coefficient of thermal expansion of the metallic plate matches that of GaN layer. The GaN layer is bonded to the metallic plate with bonding metal. The bonding metal not only bonds the GaN layer to the metallic plate but also covers the entire surface of the metallic plate to prevent corrosion of the metallic plate and optionally spontaneous nucleation of GaN on the metallic plate during the bulk GaN growth in supercritical ammonia. The bonding metal is compatible with the corrosive environment of ammonothermal growth.

Seed crystal for growth of gallium nitride bulk crystal in supercritical ammonia and fabrication method

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.

Method of growing group III nitride crystals

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 GaAlInN (0&#x2264;x1&#x2264;1, 0&#x2264;x1+y1&#x2264;1) and the seed crystal is expressed as GaAlInN (0&#x2264;x2&#x2264;1, 0&#x2264;x2+y2&#x2264;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.

Group III nitride bulk crystals and their fabrication method

Present invention discloses a high-pressure vessel of large size formed with a limited size of e.g. Ni&#x2014;Cr based precipitation hardenable superalloy. Vessel may have multiple zones. For instance, the high-pressure vessel may be divided into at least three regions with flow-restricting devices and the crystallization region is set higher temperature than other regions. This structure helps to reliably seal both ends of the high-pressure vessel, at the same time, may help to greatly reduce unfavorable precipitation of group III nitride at the bottom of the vessel. Invention also discloses novel procedures to grow crystals with improved purity, transparency and structural quality. Alkali metal-containing mineralizers are charged with minimum exposure to oxygen and moisture until the high-pressure vessel is filled with ammonia. Several methods to reduce oxygen contamination during the process steps are presented. Back etching of seed crystals and a new temperature ramping scheme to improve structural quality are disclosed.

High-pressure vessel for growing group III nitride crystals and method of growing group III nitride crystals using high-pressure vessel and group III nitride crystal

The present invention discloses methods to create higher quality group III-nitride wafers that then generate improvements in the crystalline properties of ingots produced by ammonothermal growth from an initial defective seed. By obtaining future seeds from carefully chosen regions of an ingot produced on a bowed seed crystal, future ingot crystalline properties can be improved. Specifically the future seeds are optimized if chosen from an area of relieved stress on a cracked ingot or from a carefully chosen N-polar compressed area. When the seeds are sliced out, miscut of 3-10&#xb0; helps to improve structural quality of successive growth. Additionally a method is proposed to improve crystal quality by using the ammonothermal method to produce a series of ingots, each using a specifically oriented seed from the previous ingot. When employed, these methods enhance the quality of Group III nitride wafers and thus improve the efficiency of any subsequent device.

Methods for producing improved crystallinity group III-nitride crystals from initial group III-nitride seed by ammonothermal growth

In one instance, the invention provides a method of growing bulk crystal of group III nitride using a seed crystal selected by (a) measuring x-ray rocking curves of a seed crystal at more than one point, (b) quantifying the peak widths of the measured x-ray rocking curves, and (c) evaluating the distribution of the quantified peak widths. The invention also includes the method of selecting a seed crystal for growing bulk crystal of group III nitride. 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 selected by the method above.

Seed selection and growth methods for reduced-crack group III nitride bulk crystals

Bulk crystal of group III nitride having thickness greater than 1 mm with improved crystal quality, reduced lattice bowing and/or reduced crack density and methods of making. Bulk crystal has a seed crystal, a first crystalline portion grown on the first side of the seed crystal and a second crystalline portion grown on the second side of the seed crystal. Either or both crystalline portions have an electron concentration and/or an oxygen concentration similar to the seed crystal. The bulk crystal can have an additional seed crystal, with common faces (e.g. same polarity, same crystal plane) of seed crystals joined so that a first crystalline part grows on the first face of the first seed crystal and a second crystalline part grows on the first face of the second seed crystal. Each crystalline part's electron concentration and/or oxygen concentration may be similar to its corresponding seed crystal.

Group III nitride bulk crystals and fabrication method

The present invention discloses a production method for group III nitride ingots or pieces such as wafers. To solve the coloration problem in the wafers grown by the ammonothermal method, the present invention composed of the following steps; growth of group III nitride ingots by the ammonothermal method, slicing of the ingots into wafers, annealing of the wafers in a manner that avoids dissociation or decomposition of the wafers. This annealing process is effective to improve transparency of the wafers and/or otherwise remove contaminants from wafers.

Method for producing group III-nitride wafers and group III-nitride wafers

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 GaAlInN (0&#x2266;x1&#x2266;1, 0&#x2266;x1+y1&#x2266;1) and the seed crystal is expressed as GaAlInN (0&#x2266;x2&#x2266;1, 0&#x2266;x2+y2&#x2266;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.

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.

Group III nitride wafer and its production method

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. The new HVPE reactor which can grow gallium nitride crystals for more than 1 day may produce enough source material for ammonothermal growth. Single crystalline gallium nitride and polycrystalline gallium nitride from the HVPE reactor may be used as seed crystals and a nutrient for ammonothermal group III-nitride growth.

Growth reactor for gallium-nitride crystals using ammonia and hydrogen chloride

The present invention discloses a semi-insulating wafer of GaAlInN (0&#x2266;x&#x2266;1, 0&#x2266;x+y&#x2266;1) which is doped with bismuth (Bi). The semi-insulating wafer has the resistivity of 10ohm-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 10cm. The invention also disclose the method of fabricating the semi-insulating group III nitride bulk crystals and wafers.

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Buellton, CA, United States of America

Edward Letts