Epitaxial structure of semiconductor device and method of manufacturing the same

An epitaxial structure of a semiconductor device, the structure comprising:

• a substrate;
• and
• an epitaxial layer located on a side of the substrate, the epitaxial layer comprising a nucleation layer located on a side of the substrate and a buffer layer locate on a side of the nucleation layer opposite the substrate,
• wherein a thickness of the buffer layer is inversely proportional to a thickness of the nucleation layer,
• wherein the thickness of the nucleation layer is h1 and the thickness of the buffer layer is h2,
• wherein 0.1/h2≤h1≤0.25/h2,
• wherein the buffer layer comprises a first-type buffer layer and a second-type buffer layer arranged in layers, wherein the first-type buffer layer is located on a side close to the substrate, and wherein a doping concentration of the first-type buffer layer is greater than a doping concentration of the second-type buffer layer,
• wherein the first-type buffer layer comprises a first A buffer layer and a first B buffer layer arranged in layers, wherein the first A buffer layer is located on a side close to the substrate, and wherein a doping concentration of the first A buffer layer is greater than or equal to the doping concentration of the first B buffer layer,
• wherein the second-type buffer layer comprises a second A buffer layer and a second B buffer layer arranged in layers, wherein the second A buffer layer is located on a side close to the substrate, and wherein a doping concentration of the second A buffer layer is greater than a doping concentration of the second B buffer layer,
• wherein the first A buffer layer, the first B buffer layer, the second A buffer layer, and the second B buffer layer are all doped with carbon ions,
• wherein a doping concentration of the carbon ions in the first A buffer layer is a first doping concentration C1, wherein a doping concentration of the carbon ions in the first B buffer layer is a second doping concentration C2, wherein a doping concentration of the carbon ions in the second A buffer layer is a third doping concentration C3, wherein a doping concentration of the carbon ions in the second B buffer layer is a fourth doping concentration C4, and wherein C1>C2=C3>C4,
• wherein the first A buffer layer and the first B buffer layer are further doped with iron ions, while the second A buffer layer and the second B buffer layer are not doped with iron ions,
• a doping concentration of the iron ions in the first A buffer layer is a fifth doping concentration C5, a doping concentration of the iron ions in the first B buffer layer is a sixth doping concentration C6, and wherein the fifth doping concentration is the same as the sixth doping concentration,
• wherein C1/C5=(0.5˜1.2)/10,
• wherein C2/C6=(0.1˜0.3)/10, and
• wherein C4/C3=(1˜2)/10.