Patent ID: 8169004

Claim:
A compound semiconductor epitaxial substrate having a HEMT structure, comprising a single crystal substrate, a lattice mismatch compound semiconductor layer and a stress compensation layer, wherein the lattice mismatch compound semiconductor layer and the stress compensation layer are disposed on the identical surface side of the single crystal substrate, there is no occurrence of lattice relaxation in the lattice mismatch compound semiconductor layer, as well as the stress compensation layer, and Ls representing the lattice constant of the single crystal substrate, Lm representing the lattice constant of the lattice mismatch compound semiconductor layer, and Lc representing the lattice constant of the stress compensation layer satisfy the formula (1a) or (2a) Lm<Ls<Lc (1a) Lm>Ls>Lc (2a); wherein the lattice constants of Lm, Ls, and Lc are the values associated with each individual layer at natural, unstrained condition; wherein the compound semiconductor epitaxial substrate comprises the single crystal layer, a buffer layer, an electron supply layer made of AlGaAs, a spacer layer, the lattice mismatch compound semiconductor layer in this order, and a part of the buffer layer is replaced with the stress compensation layer.