Group iii nitride substrate, method of making, and method of use

Abstract

Embodiments of the present disclosure include techniques related to techniques for processing materials for manufacture of group-III metal nitride and gallium based substrates. More specifically, embodiments of the disclosure include techniques for growing large area substrates using a combination of processing techniques. Merely by way of example, the disclosure can be applied to growing crystals of GaN, AlN, InN, InGaN, AlGaN, and AlInGaN, and others for manufacture of bulk or patterned substrates. Such bulk or patterned substrates can be used for a variety of applications including optoelectronic and electronic devices, lasers, light emitting diodes, solar cells, photo electrochemical water splitting and hydrogen generation, photodetectors, integrated circuits, and transistors, and others.

What is claimed is: 
     
         1 . A method for forming a group III metal containing nitride free-standing crystal, comprising:
 depositing a patterned mask layer on a first surface of a substrate, wherein
 the substrate is selected from one of single-crystalline group-III metal nitride, gallium-containing nitride, and gallium nitride, and has a concentration of threading dislocations less than 10 8  cm −2  and a concentration of stacking faults less than 10 4  cm −1 , and 
 the patterned mask layer comprises an array of openings that have a pitch in a first direction between 5 micrometers and 20 millimeters; 
   removing portions of the substrate exposed within the array of openings to form trenches in the substrate, the trenches having a depth below the first surface of greater than 50 micrometers; and   performing a bulk crystal growth process using the substrate as a seed crystal.   
     
     
         2 . The method of  claim 1 , wherein the trenches have a width between 10 micrometers and 200 micrometers and a length between 100 micrometers and 50 millimeters. 
     
     
         3 . The method of  claim 1 , wherein the patterned mask layer comprises an inert layer overlying an adhesion layer, wherein the adhesion layer comprises one or more of Ti, TiN, TiN y , TiSi 2 , Ta, TaN y , Al, Ge, Al x Ge y , Cu, Si, Cr, V, Ni, W, TiW x , TiW x N y  and has a thickness between 1 nanometer and 1 micrometer and the inert layer comprises one or more of Au, Ag, Pt, Pd, Rh, Ru, Ir, Ni, Cr, V, Ti, or Ta and has a thickness between 10 nanometers and 100 micrometers. 
     
     
         4 . The method of  claim 3 , wherein the pattered mask layer further comprises a diffusion barrier layer between the adhesion layer and the inert layer, the diffusion barrier layer comprising one or more of TiN, TiN y , TiSi 2 , W, TiW x , TiN y , WN y , TaN y , TiW x N y , TiW x Si z N y , TiC, TiCN, Pd, Rh, or Cr, and having a thickness between 1 nanometer and 10 micrometers. 
     
     
         5 . The method of  claim 1 , wherein the bulk crystal growth process comprises:
 placing the substrate in a sealable container along with a group III metal source, a mineralizer and ammonia;   heating the sealable container to a temperature above 400 degrees Celsius, thereby causing an ammonothermal group III metal nitride material to grow within the plurality of trenches, within the plurality of openings, outward through the plurality of openings, and subsequently laterally over the patterned mask; and   pressurizing it to a pressure above 50 megapascal for a duration of at least 100 hours.   
     
     
         6 . The method of  claim 1 , wherein the bulk crystal growth process causes a group III metal nitride material to grow laterally over the patterned mask layer and coalesce to form one or more coalescence fronts, wherein the one or more coalescence fronts comprise a pattern of locally-approximately-linear arrays of threading dislocations that have a concentration between 5 cm −1  and 10 5  cm −1 . 
     
     
         7 . The method of  claim 1 , wherein the openings in the patterned mask layer are formed by a lithography process and the trenches underlying the openings are formed by a wet etching process. 
     
     
         8 . The method of  claim 1 , wherein the openings in the patterned mask layer and the trenches are formed by a laser process. 
     
     
         9 . The method of  claim 8 , wherein the laser process comprises scanning over individual locations repetitively to form openings in the mask layer and trenches having predetermined dimensions. 
     
     
         10 . The method of  claim 8 , wherein the laser process comprises scanning over an entire pattern on the first surface repetitively to form openings in the mask layer and trenches having predetermined dimensions. 
     
     
         11 . The method of  claim 8 , wherein residual damage in the trenches is removed by a wet etching or by a photoelectrochemical etching process. 
     
     
         12 . The method of  claim 1 , wherein the substrate comprises single-crystal gallium nitride, the first surface has a crystallographic orientation within about 5 degrees of (000-1) -c-plane, and the trenches are formed by an etching process comprising H 3 PO 4 . 
     
     
         13 . The method of  claim 1 , wherein the openings of the patterned mask layer has a shape selected from round, square, rectangular, triangular, and hexagonal, and has a size between 1 micrometer and 5 millimeters. 
     
     
         14 . The method of  claim 1 , wherein the openings of the patterned mask layer comprise slits, the slits having a width between 1 micrometer and 5 millimeters and a length between 5 micrometers and 20 millimeters. 
     
     
         15 . The method of  claim 14 , wherein adjacent rows of slits are displaced along a direction of the slits with respect to one another. 
     
     
         16 . The method of  claim 14 , wherein the arrangement of the slits reflect a hexagonal symmetry of the substrate. 
     
     
         17 . The method of  claim 1 , wherein the trenches penetrate the entire thickness of the substrate. 
     
     
         18 . The method of  claim 6 , further comprising forming a free-standing group III metal nitride boule from the laterally-grown group III metal nitride material. 
     
     
         19 . The method of  claim 18 , further comprising preparing at least one free-standing group III metal nitride substrate from the free-standing group III metal nitride boule. 
     
     
         20 . The method of  claim 1 , wherein the bulk crystal growth is initiated from sidewalls of the trenches.