There is provided a nitride crystal substrate constituted by group-III nitride crystal, containing n-type impurities, with an absorption coefficient being approximately expressed by equation (1) by a least squares method in a wavelength range of at least 1 m or more and 3.3 m or less.

=N.sub.eK.sup.a(1)

(where 1.510.sup.19K6.010.sup.19, a=3),

here, a wavelength is (m), an absorption coefficient of the nitride crystal substrate at 27 C. is (cm.sup.1), a carrier concentration in the nitride crystal substrate is N.sub.e (cm.sup.3), and K and a are constants, wherein an error of an actually measured absorption coefficient with respect to the absorption coefficient obtained from equation (1) at a wavelength of 2 m is within 0.1, and in a reflection spectrum measured by irradiating the nitride crystal substrate with infrared light, there is no peak with a peak top within a wavenumber range of 1,200 cm.sup.1 or more and 1,500 cm.sup.1 or less.

A gallium-containing nitride crystals are disclosed, comprising: a top surface having a crystallographic orientation within about 5 degrees of a plane selected from a (0001)+c-plane and a (000-1)c-plane; a substantially wurtzite structure; n-type electronic properties; an impurity concentration of hydrogen greater than about 510.sup.17 cm.sup.3, an impurity concentration of oxygen between about 210.sup.17 cm.sup.3 and about 110.sup.20 cm.sup.3, an [H]/[O] ratio of at least 0.3; an impurity concentration of at least one of Li, Na, K, Rb, Cs, Ca, F, and Cl greater than about 110.sup.16 cm.sup.3, a compensation ratio between about 1.0 and about 4.0; an absorbance per unit thickness of at least 0.01 cm.sup.1 at wavenumbers of approximately 3175 cm.sup.1, 3164 cm.sup.1, and 3150 cm.sup.1, and wherein, at wavenumbers between about 3200 cm.sup.1 and about 3400 cm.sup.1 and between about 3075 cm.sup.1 and about 3125 cm.sup.1, said gallium-containing nitride crystal is essentially free of infrared absorption peaks having an absorbance per unit thickness greater than 10% of the absorbance per unit thickness at 3175 cm.

A gallium-containing nitride crystals are disclosed, comprising: a top surface having a crystallographic orientation within about 5 degrees of a plane selected from a (0001) +c-plane and a (000-1) ?c-plane; a substantially wurtzite structure; n-type electronic properties; an impurity concentration of hydrogen greater than about 5?10.sup.17 cm.sup.?3; an impurity concentration of oxygen between about 2?10.sup.17 cm.sup.?3 and about 1?10.sup.20 cm.sup.?3; an [H]/[O] ratio of at least 0.3; an impurity concentration of at least one of Li, Na, K, Rb, Cs, Ca, F, and Cl greater than about 1?10.sup.16 cm.sup.?3; a compensation ratio between about 1.0 and about 4.0; an absorbance per unit thickness of at least 0.01 cm.sup.?1 at wavenumbers of approximately 3175 cm.sup.?1, 3164 cm.sup.?1, and 3150 cm.sup.?1; and wherein, at wavenumbers between about 3200 cm.sup.?1 and about 3400 cm.sup.?1 and between about 3075 cm.sup.?1 and about 3125 cm.sup.?1, said gallium-containing nitride crystal is essentially free of infrared absorption peaks having an absorbance per unit thickness greater than 10% of the absorbance per unit thickness at 3175 cm.

A method of processing a gallium nitride substrate, includes providing a gallium nitride substrate, polishing a surface of the gallium nitride substrate, and cleaning the polished surface of the gallium nitride substrate. The polished surface includes a GaL/CK peak intensity ratio in energy dispersive X-ray microanalysis (EDX) spectrum which is not less than 2, the EDX spectrum being obtained in an EDX of the surface of the gallium nitride substrate using a scanning electron microscope (SEM) at an accelerating voltage of 3 kV.

In one instance, the seed crystal of this invention provides a nitrogen-polar c-plane surface of a GaN layer supported by a metallic plate. The coefficient of thermal expansion of the metallic plate matches that of GaN layer. The GaN layer is bonded to the metallic plate with bonding metal. The bonding metal not only bonds the GaN layer to the metallic plate but also covers the entire surface of the metallic plate to prevent corrosion of the metallic plate and optionally spontaneous nucleation of GaN on the metallic plate during the bulk GaN growth in supercritical ammonia. The bonding metal is compatible with the corrosive environment of ammonothermal growth.

The present invention relates to a composite material for use as a thermal interface material between a heat source and a heat sink. The present invention also relates to the method of synthesizing such a composite material. The composite material has high thermal conductivity, low thermal resistance and functions as an adhesive.

A process of preparing polycrystalline group III nitride chunks comprising the steps of (a) placing a group III metal inside a source chamber; (b) flowing a halogen-containing gas over the group III metal to form a group III metal halide; (c) contacting the group III metal halide with a nitrogen-containing gas in a deposition chamber containing a foil, the foil comprising at least one of Mo, W, Ta, Pd, Pt, Ir, or Re; (d) forming a polycrystalline group III nitride layer on the foil within the deposition chamber; (e) removing the polycrystalline group III nitride layer from the foil; and (f) comminuting the polycrystalline group III nitride layer to form the polycrystalline group III nitride chunks, wherein the removing and the comminuting are performed in any order or simultaneously.

A gallium-containing nitride crystals comprising: a top surface having a crystallographic orientation within 5 degrees of a plane selected from a (0001) +c-plane and a (000-1) ?c-plane; a substantially wurtzite structure; n-type electronic properties; an impurity concentration of hydrogen >5?10.sup.17 cm.sup.?3; an impurity concentration of oxygen between 2?10.sup.17 cm.sup.?3 and 1?10.sup.20 cm.sup.?3; an [H]/[O] ratio of at least 0.3; an impurity concentration of at least one of Li, Na, K, Rb, Cs, Ca, F, and Cl >1?10.sup.16 cm.sup.?3; a compensation ratio between 1.0 and 4.0; an absorbance per unit thickness of at least 0.01 cm.sup.?1 at wavenumbers of 3175 cm.sup.?1, 3164 cm.sup.?1, and 3150 cm.sup.?1; and wherein, at wavenumbers between 3200 cm.sup.?1 and 3400 cm.sup.?1 and between 3075 cm.sup.?1 and 3125 cm.sup.?1, said gallium-containing nitride crystal is essentially free of infrared absorption peaks having an absorbance per unit thickness >10% of the absorbance per unit thickness at 3175 cm.sup.?1.

There is provided a nitride crystal substrate made of a nitride crystal with a diameter of 100 mm or more, having on its main surface: a continuous high dislocation density region and a plurality of low dislocation density regions divided by the high dislocation density region, with the main surface not including a polarity inversion domain.

A GaN-on-Si device structure and a method of fabrication are disclosed for improved die yield and device reliability of high current/high voltage lateral GaN transistors. A plurality of conventional GaN device structures comprising GaN epi-layers are fabricated on a silicon substrate (GaN-on-Si die). After processing of on-chip interconnect layers, a trench structure is defined around each die, through the GaN epi-layers and into the silicon substrate. A trench cladding is provided on proximal sidewalls, comprising at least one of a passivation layer and a conductive metal layer. The trench cladding extends over exposed surfaces of the GaN epi-layers, over the interface region with the substrate, and over the exposed surfaces of the interconnect layers. This structure reduces risk of propagation of dicing damage and defects or cracks in the GaN epi-layers into active device regions. A metal trench cladding acts as a barrier for electro-migration of mobile ions.