US 12,421,621 B2
Underlying substrate
Hiroshi Fukui, Obu (JP); Morimichi Watanabe, Nagoya (JP); and Jun Yoshikawa, Nagoya (JP)
Assigned to NGK INSULATORS, LTD., Nagoya (JP)
Filed by NGK INSULATORS, LTD., Nagoya (JP)
Filed on Jul. 28, 2021, as Appl. No. 17/443,828.
Application 17/443,828 is a continuation of application No. PCT/JP2020/006312, filed on Feb. 18, 2020.
Claims priority of application No. 2019-063602 (JP), filed on Mar. 28, 2019.
Prior Publication US 2021/0355602 A1, Nov. 18, 2021
Int. Cl. C30B 29/16 (2006.01); C30B 25/18 (2006.01); C30B 29/40 (2006.01); C30B 29/66 (2006.01)
CPC C30B 25/183 (2013.01) [C30B 29/16 (2013.01); C30B 29/406 (2013.01); C30B 29/66 (2013.01)] 12 Claims
OG exemplary drawing
 
1. A ground substrate comprising an orientation layer used for crystal growth of a nitride or oxide of a Group 13 element,
wherein a front surface of the orientation layer on a side used for the crystal growth is composed of a material having a corundum-type crystal structure having an a-axis length and/or c-axis length larger than that of sapphire,
wherein a plurality of pores are present in the orientation layer and the number of pores in the orientation layer is 1.0×104/cm2 to 1.0×109/cm2,
wherein the material having the corundum-type crystal structure contains one or more materials selected from the group consisting of α-Cr2O3, α-Fe2O3, and α-Ti2O3 or a solid solution thereof, or a solid solution containing α-Al2O3 and one or more materials selected from the group consisting of α-Cr2O3, α-Fe2O3, and α-Ti2O3,
wherein in the orientation layer, the number of pores in a surface layer region including the front surface is smaller than the number of pores in a deep layer region away from the front surface, and
wherein the surface layer region represents 20% of a thickness of the orientation layer, and the deep layer region represents 80% of the remaining thickness of the orientation layer.