A synthesis method which consists of depositing a monocrystalline film (from vapor-phase precursors) on a monocrystalline substrate.

A special method in CVD, called Epitaxy or Epitaxial Layer Deposition or Vapor-Phase Epitaxy (VPE), has only a single-crystal form as the deposited layer.

This process is usually carried out for certain combinations of substrate and layer materials and under special deposition conditions.

In this process, a reaction chamber is introduced in which the materials to be deposited are passed through.

These materials should be in the gaseous or vapor phase and react on or near the surface of the substrates, which are at some elevated temperature.

This produces a chemical reaction and forms atoms or molecules that are to be deposited on entire substrate surface.

The epitaxial layer deposition takes place in a chamber called an epitaxial reactor. There are three basic types of reactors.

1. Horizontal Reactor
2. Vertical Reactor and
3. Cylindrical Reactor

So epitaxial reactor can be logically divided into 3 sections:

1. Gas delivery system which provides species in accurately metered form.
2. Reaction chamber where these species are transported to substrate.
3. Effluent handling system.

Some varieties of VPE are – Chloride VPE, Hydroid VPE and Organometallic VPE.