▎ 摘　　要

NOVELTY - Preparing gallium nitride single crystal substrate utilizing edge metal mask technology, comprises (i) providing composite epitaxial substrate (ii) using hydride vapor phase epitaxy (HVPE) technology in HVPE cavity, epitaxially growing GaN single crystal sacrificial layer on the positive surface of composite epitaxial substrate, (iii) maintaining the space position of composite epitaxial substrate grown with GaN single crystal sacrificial layer in HVPE cavity unchanged, introducing the thermal stress in horizontal direction through time domain temperature gradient, (iv) taking out the composite structure of single crystal graphene and metal lattice polar GaN single crystal template from HVPE cavity, then heating the HVPE cavity, diameter expansion growth of the GaN single crystal thick film is carried out on the front surface of the GaN single crystal sacrificial layer, and (v) trimming GaN single crystal thick film by chemical mechanical method to obtain final product. USE - The method is useful for preparing gallium nitride single crystal substrate utilizing edge metal mask technology. ADVANTAGE - The gallium nitride single crystal substrate has no problems of mismatch stress accumulation and diameter shrinkage. DETAILED DESCRIPTION - Preparing gallium nitride single crystal substrate utilizing edge metal mask technology, comprises (i) providing composite epitaxial substrate in which composite epitaxial substrate includes gallium nitride (GaN) epitaxial film with nitrogen lattice polarity without biaxial stress, pleated multilayer single crystal graphene and GaN single crystal template of metal lattice polarity from top to bottom, where GaN epitaxial film with nitrogen lattice polarity is positive surface of composite epitaxial substrate, depositing a metal mask ring on the positive surface edge of composite epitaxial substrate in which metal mask ring is annular, located at edge of the composite epitaxial substrate, fully and stably connected with composite epitaxial substrate, outer diameter of metal mask ring is equal to the diameter of composite epitaxial substrate, (ii) using hydride vapor phase epitaxy (HVPE) technology in HVPE cavity, epitaxially growing GaN single crystal sacrificial layer on the positive surface of composite epitaxial substrate, during epitaxial process, gallium metal atom provided by group III source is chemically reacted with nitrogen atom provided by nitrogen source, metal mask ring catalyzes decomposition of ammonia gas, thus block the nitride adhesion growth on metal mask ring, inhibiting the epitaxial nitride on composite epitaxial substrate extending to metal mask ring direction of edge anisotropy growth, GaN single crystal sacrificial layer confinement growth in surrounding area of metal mask ring, GaN single crystal sacrificial layer is not connected with any direction of GaN single crystal template of metal lattice polarity of composite epitaxial substrate, further adjusting the flow rate of III group source and nitrogen source, controlling the growth rate of GaN single crystal sacrificial layer, and controlling the thickness of GaN single crystal sacrificial layer to be lower than the height of metal mask ring, (iii) maintaining the space position of composite epitaxial substrate grown with GaN single crystal sacrificial layer in HVPE cavity unchanged, quickly cooling the environment temperature to low temperature range, introducing the thermal stress in horizontal direction through time domain temperature gradient, making the bonding force of GaN epitaxial film with nitrogen lattice polarity and single crystal graphene, and bonding force between GaN single crystal template with metal lattice polarity and single crystal graphene are greater than bonding force between inner layer of single crystal graphene, decoupling the single crystal graphene between layers to obtain self-supporting GaN single crystal sacrificial layer with continuous and complete transverse and longitudinal dimensions and capable of in-situ secondary growth, composite structure composed of GaN epitaxial film with nitrogen lattice polarity and single crystal graphene, and composite structure composed of single crystal graphene and GaN single crystal template with metal lattice polarity, (iv) taking out the composite structure of single crystal graphene and metal lattice polar GaN single crystal template from HVPE cavity, then heating the HVPE cavity, diameter expansion growth of the GaN single crystal thick film is carried out on the front surface of the GaN single crystal sacrificial layer, when the total thickness of GaN single crystal thick film and GaN single crystal sacrificial layer is not greater than the height of metal mask ring, GaN single crystal thick film for confinement growth, i.e. transverse growth rate is zero, when the thickness of GaN single crystal thick film and GaN single crystal sacrificial layer is greater than height of edge metal mask ring, limiting action of metal mask ring is weakened, GaN single crystal thick film for transverse expanding growth to obtain GaN single crystal thick film, and (v) trimming GaN single crystal thick film by chemical mechanical method to obtain final product.