A window assembly heat transfer system is disclosed in which a window member has a selected transparency to monitored or sensed light wavelengths. One or more passages are provided in the window member for flowing a single-phase or two-phase heat transfer fluid, the passages being optically non-transparent to the monitored or sensed light wavelengths. A mechanism allows either evaporation or condensation of the fluid and/or balancing of a flow of the fluid within the passages. In one embodiment, the window assembly can be made by producing passages in a top surface of a first single plate, optionally producing passages in a bottom surface of a second single plate and bonding the top surface of the first plate to a bottom surface of a second single plate to form the window member with the passage or passages. In another embodiment, the window assembly can be made by providing a core around which the window member material is grown and thereafter removing the core to produce the passage or passages.

A composite substrate including a substrate and an aluminum nitride layer is provided. The aluminum nitride layer is disposed on a top surface of the substrate. Silicon is doped in the aluminum nitride layer to regulate residual stress, a film thickness of the aluminum nitride layer is less than 3.5 μm, a defect density of the aluminum nitride layer is less than or equal to 5×10.sup.9/cm.sup.2, and a root mean square roughness of the top surface, facing away from the substrate, of the aluminum nitride layer is less than 3 nm. A manufacturing method of a composite substrate is also provided.

A composite substrate including a substrate and an aluminum nitride layer is provided. The aluminum nitride layer is disposed on a top surface of the substrate. Silicon is doped in the aluminum nitride layer to regulate residual stress, a film thickness of the aluminum nitride layer is less than 3.5 μm, a defect density of the aluminum nitride layer is less than or equal to 5×10.sup.9/cm.sup.2, and a root mean square roughness of the top surface, facing away from the substrate, of the aluminum nitride layer is less than 3 nm. A manufacturing method of a composite substrate is also provided.

In a method for manufacturing a device fabrication wafer, an SiC epitaxial wafer that is an SiC wafer 40 having a monocrystalline SiC epitaxial layer formed thereon is subjected to a basal plane dislocation density reduction step of reducing the density of basal plane dislocations existing in the epitaxial layer of the SiC epitaxial wafer, to thereby manufacture the device fabrication wafer for use to fabricate a semiconductor device. In the basal plane dislocation density reduction step, the SiC epitaxial wafer is heated under Si vapor pressure for a predetermined time necessary to reduce the density of basal plane dislocations, without formation of a cap layer on the SiC epitaxial wafer, so that the density of basal plane dislocations is reduced with suppression of surface roughening.

A method of manufacturing a group III nitride crystal according to a first aspect includes: preparing a seed substrate; generating a group III element oxide gas; supplying the group III element oxide gas; supplying a nitrogen element-containing gas; supplying an oxidizing gas containing nitrogen element containing at least one selected from the group consisting of NO gas, NO.sub.2 gas, N.sub.2O gas, and N.sub.2O.sub.4 gas; and growing the group III nitride crystal on the seed substrate.

A method of manufacturing a group III nitride crystal according to a first aspect includes: preparing a seed substrate; generating a group III element oxide gas; supplying the group III element oxide gas; supplying a nitrogen element-containing gas; supplying an oxidizing gas containing nitrogen element containing at least one selected from the group consisting of NO gas, NO.sub.2 gas, N.sub.2O gas, and N.sub.2O.sub.4 gas; and growing the group III nitride crystal on the seed substrate.

A method of controlling contamination of a vapor deposition apparatus includes: a wafer loading step of loading a wafer for contamination evaluation into a chamber of the vapor deposition apparatus; a heat treatment step of heat treating the wafer for contamination evaluation at a heat treatment temperature of 1190° C. or more at a hydrogen flow rate of 30 slm or less; a wafer unloading step of unloading the wafer for contamination evaluation from the inside of the chamber; and a wafer contamination evaluation step of evaluating a level of metal contamination of the wafer for contamination evaluation. In a method of producing an epitaxial wafer, epitaxial growth is performed using a vapor deposition apparatus whose contamination is controlled by the contamination controlling method.

A group-III nitride substrate includes: a first region having a first impurity concentration in a polished surface; and a second region having a second impurity concentration lower than the first impurity concentration in the polished surface, wherein a first dislocation density of the first region is lower than a second dislocation density of the second region.

A method of forming a layer includes introducing a Group III precursor in a reactor, introducing a hydride Group V precursor in the reactor, and introducing a metal-organic Group V precursor in the reactor to form the layer. The method can further include mixing the hydride Group V precursor and the metal-organic Group V precursor. Advantageously, the layer and method of forming the layer utilize mixed Group V precursors, improve uniformity, decrease thermal sensitivity of the end material, normalize concentration profiles of precursors, improve yield, increase manufacturing efficiency, improve control of III-V ratios (e.g., pressure, growth rate, flux), and reduce manufacturing costs.

A method of performing HVPE heteroepitaxy comprises exposing a substrate to a carrier gas, a first precursor gas, a Group II/III element, and ternary-forming gasses (V/VI group precursor), to form a heteroepitaxial growth of a binary, ternary, and/or quaternary compound on the substrate; wherein the carrier gas is Hz, wherein the first precursor gas is HCl, the Group II/III element comprises at least one of Zn, Cd, Hg, Al, Ga, and In; and wherein the ternary-forming gasses comprise at least two or more of AsH.sub.3 (arsine), PH.sub.3 (phosphine), H.sub.2Se (hydrogen selenide), HzTe (hydrogen telluride), SbH.sub.3 (hydrogen antimonide, or antimony tri-hydride, or stibine), H.sub.2S (hydrogen sulfide), NH.sub.3 (ammonia), and HF (hydrogen fluoride); flowing the carrier gas over the Group II/III element; exposing the substrate to the ternary-forming gasses in a predetermined ratio of first ternary-forming gas to second ternary-forming gas (1tf:2tf ratio); and changing the 1tf:2tf ratio over time.