Patent ID: 8664085

Claim:
A method of manufacturing a composite substrate for epitaxial-layer growth, formed by bonding together a first substrate composed of a nitride compound semiconductor, and a second substrate composed of a material that is either identical with or different from the material constituting the first substrate, the composite-substrate manufacturing method including: a step of carrying out implantation of ions through a surface of a bulk substrate composed of the nitride compound semiconductor; a step of setting said surface of the bulk substrate against the second substrate and bonding the bulk substrate and the second substrate together to obtain a bonded substrate; a step of elevating the temperature of the bonded substrate to a first temperature; a step of sustaining the first temperature for a fixed time; and a step of producing a composite substrate by severing, in such as way as to leave the first substrate, being a portion of the bulk substrate, atop the second substrate, the remaining portion of the bulk substrate from the bonded substrate; characterized in that letting the first temperature be T 1 ° C., the thermal expansion coefficient of the first substrate be A×10 −6 /° C., and the thermal expansion coefficient of the second substrate be B×10 −6 /° C., the following formula (I) is satisfied 215≦10( A−B ) 2 −10( A−B )+ T 1 ≦410 (I).