US 12,230,679 B2
Compound semiconductor substrate including nitride semiconductor layer having varying threading dislocation densities
Sumito Ouchi, Nagano (JP); Hiroki Sukuki, Nagano (JP); Mitsuhisa Narukawa, Nagano (JP); and Keisuke Kawamura, Nagano (JP)
Assigned to Air Water Inc., Osaka (JP)
Appl. No. 17/417,950
Filed by AIR WATER INC., Osaka (JP)
PCT Filed Dec. 10, 2019, PCT No. PCT/JP2019/048179
§ 371(c)(1), (2) Date Jun. 24, 2021,
PCT Pub. No. WO2020/137501, PCT Pub. Date Jul. 2, 2020.
Claims priority of application No. 2018-241389 (JP), filed on Dec. 25, 2018.
Prior Publication US 2022/0077288 A1, Mar. 10, 2022
Int. Cl. H01L 29/20 (2006.01); H01L 29/06 (2006.01); H01L 29/205 (2006.01); H01L 29/26 (2006.01); H01L 29/267 (2006.01); H01L 29/32 (2006.01); H01L 29/778 (2006.01)
CPC H01L 29/205 (2013.01) [H01L 29/0684 (2013.01); H01L 29/2003 (2013.01); H01L 29/267 (2013.01); H01L 29/32 (2013.01); H01L 29/778 (2013.01); H01L 2924/13064 (2013.01)] 9 Claims
OG exemplary drawing
 
1. A compound semiconductor substrate comprising:
a Si substrate,
a first nitride semiconductor layer containing Al formed on the Si substrate, as a graded layer in which an Al concentration decreases as a distance from the Si substrate increases along a thickness direction,
a second nitride semiconductor layer formed on the first nitride semiconductor layer and having a lower average Al concentration than the average Al concentration of the first nitride semiconductor layer, and
a third nitride semiconductor layer containing Al formed on the second nitride semiconductor layer and having a higher average Al concentration than the average Al concentration of the second nitride semiconductor layer, wherein
a threading dislocation density at any position in a thickness direction within the third nitride semiconductor layer is lower than a threading dislocation density at any position in a thickness direction within the first nitride semiconductor layer,
at least a part of a threading dislocation that existed in the first nitride semiconductor layer is covered by the second nitride semiconductor layer, and
a boundary face between the first nitride semiconductor layer and the second nitride semiconductor layer is a sliding surface.