Method for synthesis of high quality large area bulk gallium based crystals
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 gallium based seed crystal, wherein
the gallium based seed crystal comprises at least one of a +c-plane surface and a −c-plane surface, and
at least one of the +c-plane surface and the −c-plane surface is bounded by four m-plane edges; and
subjecting the gallium based seed crystal to an ammonothermal growth process to cause the gallium based seed crystal to grow in at least one of a +c direction and a −c direction by at least about 5 mm to form a c-grown gallium based crystal comprising at least four m-plane surfaces and at least one ±c-plane surface, wherein
at least two of the at least four m-plane surfaces of the c-grown gallium based crystal each have an area larger than the at least one ±c-plane surface of the c-grown gallium based crystal.
2. The method of claim 1 , wherein each of the at least one of the +c-plane surface and the −c-plane surface of the gallium based seed crystal has a length that is parallel to at least one of the four m-plane edges and is perpendicular to a width, and
the length is larger than the width by a factor of 5 or more.
3. The method of claim 1 , wherein the c-grown gallium based crystal has 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.
4. The method of claim 1 , wherein the c-grown gallium based crystal has 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.
5. The method of claim 1 , wherein the c-grown gallium based crystal has 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.
6. The method of claim 1 , wherein the c-grown gallium based crystal is characterized by a FWHM of a 1-100 x-ray rocking curve of at least one of the at least four m-plane surfaces below 50 arcsec, a dislocation density on at least one large-area m-plane surface below 10 6 cm −2 , and a dislocation density through a c-plane in the c-grown gallium based crystal below about 10 5 cm −2 .
7. The method of claim 1 , wherein the c-grown gallium based 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 .
8. The method of claim 1 , wherein the c-grown gallium based crystal has a crystallographic radius of curvature greater than about 20 meters.
9. The method of claim 1 , further comprising slicing the c-grown gallium based crystal approximately substantially parallel to a large area surface to form one or more wafers.
10. The method of claim 1 , further comprising utilizing the c-grown gallium based crystal or a wafer prepared therefrom as a seed crystal or substrate for further bulk crystal growth.
11. The method of claim 9 , wherein the one or more wafers comprise 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.
12. The method of claim 11 , 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, a thyristor, a Schottky rectifier, 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.
13. The method of claim 1 , wherein the c-grown gallium based crystal comprises at least two semipolar {10-11} surfaces and at least two semipolar {10-1-1} surfaces, wherein the total area of the at least two semipolar {10-1-1} surfaces is larger, by a factor of at least 1.5, than the total area of the at least two semipolar {10-11} surfaces.
14. 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).
15. The method of claim 1 , wherein the ammonothermal growth process is performed at a temperature of at least 650 degrees Celsius.
16. The method of claim 10 , further comprising
preparing one or more wafers from the seed crystal formed by the further bulk crystal growth.
17. The method of claim 10 , wherein the further bulk crystal growth comprises HVPE growth.
18. The method of claim 1 , wherein the gallium based seed is prepared by a process using a c-plane GaN layer that was formed on a sapphire or gallium arsenide substrate, with a thickness of at least 1 mm.
19. The method of claim 16 , wherein the one or more wafers comprise 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. A method for forming a gallium based crystal, comprising:
providing a first gallium based seed crystal, wherein
the first gallium based seed crystal comprises at least one of a +c-plane surface and a −c-plane surface, has a length along at least one of the edges of the +c-plane surface or the −c plane surface that is larger than a width that is perpendicular to the length by a factor of 5 or more, and was prepared from a gallium-based crystal that was grown by an ammonothermal process in at least one a-direction on a second gallium based seed crystal having a maximum dimension in an m-direction that is greater than a maximum dimension in one of a +c and a −c directions; and
subjecting the first gallium based seed crystal to an ammonothermal growth process to cause the gallium based seed crystal to grow in the at least one of the +c and the −c directions by at least about 5 mm to form a c-grown gallium based crystal comprising at least four m-plane surfaces and at least one ±c-plane surfaces, wherein two of the at least four m-plane surfaces each have an area larger than each of the at least one ±c-plane surfaces.