Compound semiconductor layered structure and process for preparing the same

A compound semiconductor layered structure comprising:

• i. a silicon carbide semiconductor substrate having a bottom surface and a top surface;
• and
• ii. a silicon carbide semiconductor film on top of said silicon carbide semiconductor substrate, said silicon carbide semiconductor film comprising a nonporous bottom layer, a porous core, and a nonporous top layer, whereby said bottom layer of said silicon carbide semiconductor film is in direct contact with said top surface of said silicon carbide semiconductor substrate.

Process for preparing a compound semiconductor layered structure, comprising the steps of:

• i. providing (a) a silicon carbide semiconductor substrate having a bottom surface and a top surface, and (b) a silicon carbide semiconductor film (pre-2) having a porous bottom layer (pre-21), a porous core (pre-22) and a porous top layer (pre-23);
• ii. bringing said bottom layer (pre-21) of said silicon carbide semiconductor film (pre-2) in direct contact with a top surface of said silicon carbide semiconductor substrate;
• iii. pressing said silicon carbide semiconductor film (pre-2) and said silicon carbide semiconductor substrate together at a pressure of 5 MPa to 100 MPa, and heating at a temperature between 1250° C. and 1750° C. under an inert atmosphere at a pressure of 0.5 MPa to 10 MPa.