The p-type epitaxial layer grown over an n-type substrate for fabricating a bipolar transistor will function as

Explanation:

• Epitaxy refers to the deposition of an overlayer on a crystalline substrate, where the overlayer is in registry with the substrate. The overlayer is called an epitaxial film or epitaxial layer.
• By growing a lightly doped epi layer over a heavily-doped silicon substrate, a higher breakdown voltage across the collector-substrate junction is achieved while maintaining low collector resistance,
• It also allows better control of doping concentrations of the devices.

The figure shown below shows the fabrication of a monolithic circuit in which a p-type epitaxial layer is grown onto an n-type substrate which helps in making p-type devices formed by suitable masking and diffusion and the fabricated transistor will have a p-type emitter and collector and n-type base.

Hence, option (1) is correct.