Patent ID: 9202873
Filing Date: 2015-12-01
Classification: H01L,H01S

Abstract:
1. A semiconductor wafer, comprising: a substrate having a major surface; an AlN buffer layer of AlN provided on the major surface of the substrate; a foundation layer provided on the AlN buffer layer, the foundation layer comprising a nitride semiconductor comprising Al and Ga; a first high Ga composition layer provided on the foundation layer, the first high Ga composition layer comprising the nitride semiconductor comprising Ga; a high Al composition layer provided on the first high Ga composition layer, the high Al composition layer comprising the nitride semiconductor comprising Al, a Ga composition ratio of the high Al composition layer being lower than a Ga composition ratio of the first high Ga composition layer; a low Al composition layer provided on the high Al composition layer, the low Al composition layer comprising the nitride semiconductor comprising Al and Ga, a Ga composition ratio of the low Al composition layer being lower than the Ga composition ratio of the first high Ga composition layer, an Al composition ratio of the low Al composition layer being lower than an Al composition ratio of the high Al composition layer; an intermediate unit provided on the low Al composition layer, the intermediate unit comprising a nitride comprising at least one element selected from the group consisting of Si, Mg, and B, a thickness of the intermediate unit being not less than a 0.2 atom layer and not more than 3 nanometers; and a second high Ga composition layer provided on the intermediate unit, the second high Ga composition layer comprising the nitride semiconductor comprising Ga, a Ga composition ratio of the second high Ga composition layer being higher than the Ga composition ratio of the low Al composition layer, the first high Ga composition layer having a first tensile strain, the second high Ga composition layer having a second tensile strain larger than the first tensile strain, or the first high Ga composition layer having a first compressive strain, the second high Ga composition layer having a second-compressive strain smaller than the first compressive strain.