GaN SUBSTRATE, PRODUCTION METHOD THEREOF, PRODUCTION METHOD OF GaN LAYER-BONDED SUBSTRATE, AND PRODUCTION METHOD OF SEMICONDUCTOR DEVICE

PROBLEM TO BE SOLVED: To provide a GaN substrate requiring little machining allowance and permitting uniform and easy machining, a production method thereof, a production method of a GaN layer-bonded substrate using such GaN substrate, and a production method of a semiconductor device using such GaN layer-bonded substrate. SOLUTION: The GaN substrate 20 includes a first region 20j and a second region 20i higher than the first region 20j in a Ga/N compositional ratio, wherein the second region 20i ranges from a depth of D-ΔD to a depth of D+ΔD with respect to its center at a depth of a predetermined value D from one principal plane 20m, the difference between the Ga/N compositional ratio at the depth D and that at the depth ≥D+4ΔD in the first region 20j is three times the difference between the Ga/N compositional ratio at the depth D+ΔD and that at the depth ≥D+4ΔD in the first region 20j, and the Ga/N compositional ratio in the second region 20i is at least 1.05 times the Ga/N compositional ratio at the depth ≥D+4ΔD in the first region 20j, so that the GaN substrate 20 is easily separated at the second region 20i when energy is externally applied thereto. COPYRIGHT: (C)2010,JPO&INPIT