Method for synthesis of high quality large area bulk gallium based crystals
View Patent ↗A large area nitride crystal, comprising gallium and nitrogen, with a non-polar or semi-polar large-area face, is disclosed, along with a method of manufacture. The crystal is useful as a substrate for a light emitting diode, a laser diode, a transistor, a photodetector, a solar cell, or for photoelectrochemical water splitting for hydrogen generation.
1. A method for forming a gallium based crystal, comprising:
providing a bar-shaped proto-seed, the bar-shaped proto-seed comprising a gallium based crystal having a +c surface, a −c surface and at least one surface having a crystallographic orientation within 10 degrees of an a-plane {11-20} orientation; and
subjecting the bar-shaped proto-seed to an ammonothermal growth process of a gallium based crystalline material to cause the proto-seed to grow inhomogeneously in at least one a-direction to form a gallium based crystal having at least one upper a-wing and at least one lower a-wing, wherein the upper a-wing comprises a +c surface and the upper a-wing and the lower a-wing are separated by a gap.
2. The method of claim 1 , wherein the proto-seed has impurity concentrations of oxygen (O), hydrogen (H), carbon (C), sodium (Na), and potassium (K) below about 1×10 17 cm −3 , 2×10 17 cm −3 , 1×10 17 cm 3 , 1×10 16 cm −3 , and 1×10 16 cm −3 , respectively.
3. The method of claim 1 , wherein the upper a-wing is characterized by a dislocation density below 10 4 cm −2 .
4. The method of claim 1 , wherein each of the upper a-wing and the lower a-wing are characterized by a dislocation density below 10 4 cm −2 .
5. The method of claim 1 , wherein the proto-seed is provided by removing a seed crystal structure from a thick gallium and nitrogen containing substrate made using HVPE growth or wherein the proto seed is provided by removing a seed crystal structure from a thick gallium and nitrogen containing substrate made using ammonothermal growth.
6. The method of claim 1 , further comprising separating at least one a-wing from the gallium based crystal and utilizing the separated a-wing as a seed crystal for ammonothermal crystal growth.
7. The method of claim 6 , wherein the ammonothermal crystal growth produces a substantially rhombus-shaped gallium-based crystal with large-area c+ and c-surfaces with a surface area of at least 25 mm 2 , the rhombus-shaped crystal having a top surface and a bottom surface.
8. The method of claim 7 , wherein the top and bottom surfaces of the substantially rhombus-shaped crystal have impurity concentrations of O, H, C, Na, and K between about 1×10 17 cm −3 and 1×10 19 cm −3 , between about 1×10 17 cm −3 and 2×10 19 cm −3 , below 1×10 17 cm −3 , below 1×10 16 cm −3 , and below 1×10 16 cm −3 , respectively.
9. The method of claim 7 , wherein the top and bottom surfaces of the substantially rhombus-shaped crystal have impurity concentrations of O, H, C, and at least one of Na and K between about 1×10 17 cm −3 and 1×10 19 cm −3 , between about 1×10 17 cm 3 and 2×10 19 cm −3 , below 1×10 17 cm −3 , and between about 3×10 15 cm −3 and 1×10 18 cm −3 , respectively.
10. The method of claim 7 , wherein the top and bottom surfaces of the substantially rhombus-shaped crystal have impurity concentrations of O, H, C, and at least one of F and Cl between about 1×10 17 cm −3 and 1×10 19 cm −3 , between about 1×10 17 cm −3 and 2×10 19 cm −3 , below 1×10 17 cm −3 , and between about 1×10 15 cm −3 and 1×10 17 cm −3 , respectively.
11. The method of claim 7 , wherein the substantially rhombus-shaped crystal has an infrared absorption peak at about 3175 cm −1 , with an absorbance per unit thickness of greater than about 0.01 cm −1 .
12. The method of claim 7 , wherein the substantially rhombus-shaped crystal has a crystallographic radius of curvature greater than about 20 meters.
13. The method of claim 7 , further comprising slicing the substantially rhombus-shaped crystal approximately parallel to a large area surface to form one or more wafers.
14. The method of claim 7 , further comprising utilizing the substantially rhombus-shaped crystal or a wafer prepared therefrom as a seed crystal or substrate for further bulk crystal growth.
15. A method of manufacturing a semiconductor device, comprising utilizing a wafer prepared from the gallium-based crystal of claim 1 as a substrate for manufacture of a semiconductor structure, the semiconductor structure comprising at least one Al x In y Ga (1-x-y) N epitaxial layer, where 0≦x, y, x+y≦1.
16. The method of claim 15 , further comprising using the semiconductor structure in a gallium-nitride-based electronic device or optoelectronic device, the gallium-nitride-based electronic device or optoelectronic device being selected from a light emitting diode, a laser diode, a photodetector, an avalanche photodiode, a photovoltaic, a solar cell, a cell for photoelectrochemical splitting of water, a transistor, a rectifier, and a thyristor; one of a transistor, a rectifier, a Schottky rectifier, a thyristor, a p-i-n diode, a metal-semiconductor-metal diode, high-electron mobility transistor, a metal semiconductor field effect transistor, a metal oxide field effect transistor, a power metal oxide semiconductor field effect transistor, a power metal insulator semiconductor field effect transistor, a bipolar junction transistor, a metal insulator field effect transistor, a heterojunction bipolar transistor, a power insulated gate bipolar transistor, a power vertical junction field effect transistor, a cascade switch, an inner sub-band emitter, a quantum well infrared photodetector, a quantum dot infrared photodetector, or combinations thereof.
17. The method of claim 7 , further comprising slicing the substantially rhombus-shaped crystal into at least two laterally-grown strip-shaped crystals with at least two long edges characterized by a surface orientation within about 10 degrees of an m-plane.
18. The method of claim 17 , further comprising utilizing the laterally-grown strip-shaped crystals as seeds for ammonothermal crystal growth and growing the crystals by at least 5 mm in the +/−c direction to form a c-grown crystal.
19. A method of manufacturing a semiconductor device, comprising utilizing a wafer prepared the substantially rhombus-shaped crystal of claim 7 as a substrate for manufacture of a semiconductor structure, the semiconductor structure comprising at least one Al x In y Ga (1-x-y) N epitaxial layer, where 0≦x, y, x+y≦1.
20. The method of claim 19 , further comprising using the semiconductor structure in a gallium-nitride-based electronic device or optoelectronic device, the gallium-nitride-based electronic device or optoelectronic device being selected from a light emitting diode, a laser diode, a photodetector, an avalanche photodiode, a photovoltaic, a solar cell, a cell for photoelectrochemical splitting of water, a transistor, a rectifier, and a thyristor; one of a transistor, a rectifier, a Schottky rectifier, a thyristor, a p-i-n diode, a metal-semiconductor-metal diode, high-electron mobility transistor, a metal semiconductor field effect transistor, a metal oxide field effect transistor, a power metal oxide semiconductor field effect transistor, a power metal insulator semiconductor field effect transistor, a bipolar junction transistor, a metal insulator field effect transistor, a heterojunction bipolar transistor, a power insulated gate bipolar transistor, a power vertical junction field effect transistor, a cascade switch, an inner sub-band emitter, a quantum well infrared photodetector, a quantum dot infrared photodetector, or combinations thereof.
21. The method of claim 1 , wherein the ammonothermal growth process includes the use of polycrystalline GaN material and a mineralizer comprising at least one of fluorine (F) and chlorine (Cl).
22. The method of claim 20 , wherein the ammonothermal growth process is performed at a temperature of at least 650 degrees Celsius.