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Method for achieving low defect density algan single crystal boules

a single crystal boule and defect density technology, applied in the field of single crystal growing methods, can solve the problem of relatively low growth rate at this temperature, and achieve the effect of prolonging the growth cycle, controlling the amount of ga undergoing a reaction, and limited production

Inactive Publication Date: 2009-02-26
FREIBERGER COMPOUND MATERIALS
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention provides a method and apparatus for growing bulk GaN and AlGaN single crystal boules using a modified HVPE process. The method involves using an extended Ga source and an extended Al source in a reactor, which allows for extended growth cycles without experiencing degradation in the as-grown material. The reactor includes at least one growth zone maintained at a high temperature for initiating crystalline growth and a second growth zone maintained at a lower temperature for achieving high growth rates. The reactor also includes a multi-temperature zone furnace and a repetitive growth cycle for achieving superior quality in the single crystal boule. The technical effects of the invention include controllable and limited amounts of Ga undergoing a reaction, allowing for extended growth cycles without experiencing degradation in the as-grown material, and the ability to grow large single crystal boules.

Problems solved by technology

Although the high temperature of this zone allows high quality crystal growth, the growth rate at this temperature is relatively low.

Method used

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  • Method for achieving low defect density algan single crystal boules
  • Method for achieving low defect density algan single crystal boules
  • Method for achieving low defect density algan single crystal boules

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specific embodiments

Embodiment 1

[0051] According to this embodiment of the invention, the modified HVPE process described above was used to grow thick GaN layers on SiC substrates. Suitable GaN substrates were then fabricated and used in conjunction with the modified HVPE process of the invention to grow a GaN single crystal boule. The second GaN boule was cut into wafers suitable for device applications.

[0052] In this embodiment, multiple SiC substrates of a 6H polytype were loaded into the growth zone of a reactor similar to that shown in FIG. 1. The substrates were placed on a quartz sample holder with the (0001) Si on-axis surface positioned for GaN deposition. One kilogram of Ga metal was positioned in the source boat within the Ga source tube. After purging the reactor with Ar gas to remove air, the growth zone and the Ga source zone were heated to 1100° C. and 650° C., respectively. The majority of the Ga source, however, was maintained at a temperature of less than 100° C., typically in the r...

embodiment 2

[0062] In this embodiment, a GaN seed was first fabricated as described in Embodiment 1. The 5.08 centimeter diameter (i.e., 2 inch diameter) prepared GaN seed substrates were then placed within a stainless steel, resistively heated furnace and a GaN single crystal boule was grown using a sublimation technique. GaN powder, located within a graphite boat, was used as the Ga vapor source while NH3 gas was used as the nitrogen source. The GaN seed was kept at a temperature of 1100° C. during the growth. The GaN source was located below the seed at a temperature higher than the seed temperature. The growth was performed at a reduced pressure.

[0063] The growth rate using the above-described sublimation technique was approximately 0.5 millimeters per hour. After a growth cycle of 24 hours, a 12 millimeter thick boule was grown with a maximum boule diameter of 54 millimeters. The boule was divided into 30 wafers using a diamond wire saw and the slicing and processing procedures described ...

embodiment 3

[0064] In this embodiment, bulk GaN material was grown in an inert gas flow at atmospheric pressure utilizing the hot-wall, horizontal reactor described in Embodiment 1. Six 5.08 centimeter diameter (i.e., 2 inch diameter) silicon carbide substrates of a 6H polytype, were placed on a quartz pedestal and loaded into a growth zone of the quartz reactor. The substrates were located such that the (0001) Si on-axis surfaces were positioned for GaN deposition. Approximately 0.9 kilograms of Ga (7N) was located within a quartz boat in the Ga source zone of the reactor. This channel was used for delivery of gallium chloride to the growth zone of the reactor. A second quartz tube was used for ammonia (NH3) delivery to the growth zone. A third separate quartz tube was used for HCl gas delivery to the growth zone.

[0065] The reactor was filled with Ar gas, the Ar gas flow through the reactor being in the range of 1 to 25 liters per minute. The substrates were then heated in Ar flow to a temper...

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Abstract

A method for growing bulk GaN and AlGaN single crystal boules, preferably using a modified HVPE process, is provided. The single crystal boules typically have a volume in excess of 4 cubic centimeters with a minimum dimension of approximately 1 centimeter. If desired, the bulk material can be doped during growth to achieve n-, i-, or p-type conductivity. In order to have growth cycles of sufficient duration, preferably an extended Ga source is used in which a portion of the Ga source is maintained at a relatively high temperature while most of the Ga source is maintained at a temperature close to, and just above, the melting temperature of Ga. To grow large boules of AlGaN, preferably multiple Al sources are used, the Al sources being sequentially activated to avoid Al source depletion and excessive degradation. In order to achieve high growth rates, preferably a dual growth zone reactor is used in which a first, high temperature zone is used for crystal nucleation and a second, low temperature zone is used for rapid crystal growth. Although the process can be used to grow crystals in which the as-grown material and the seed crystal are of different composition, preferably the two crystalline structures have the same composition, thus yielding improved crystal quality.

Description

CROSS REFERENCES TO RELATED APPLICATIONS [0001] The present application is a continuation of U.S. application Ser. No. 09 / 903,047 filed Jul. 9, 2001, priority of which is claimed under 35 U.S.C. § 120, which is a continuation of U.S. application Ser. No. 09 / 900,833, filed Jul. 6, 2001, priority of which is also claimed under 35 U.S.C. §120.FIELD OF THE INVENTION [0002] The present invention relates generally to semiconductor materials and, more particularly, to a method for growing bulk single crystals. BACKGROUND OF THE INVENTION [0003] Recent results in the development of GaN-based light-emitting diodes (LEDs) and laser diodes LDs) operating in the green, blue, and ultraviolet spectrum have demonstrated the tremendous scientific and commercial potential of group III nitride semiconductors (e.g., GaN, AlN, InN, and their alloys). These applications require electrically conducting substrates (e.g., GaN or AlGaN) so that a vertical device geometry can be utilized in which the electro...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H01L33/00C30B11/00C30B11/14C30B25/00C30B29/40H01L21/205
CPCC30B11/00C30B11/14C30B25/00C30B29/40C30B29/403H01L21/0262H01L21/0237H01L21/02378H01L21/02389H01L21/0254C30B29/406
Inventor MELNIK, YURISOUKHOVEEV, VITALIIVANTSOV, VLADIMIRTSVETKOV, KATIEDMITRIEV, VLADIMIR
Owner FREIBERGER COMPOUND MATERIALS
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