Metal Organic Chemical Vapour Deposition (MOCVD) is a chemical vapour deposition method used to produce thin films of single- or polycrystalline materials. It is a widely used technique in the semiconductor industry for the growth of complex semiconductor multilayer structures. MOCVD is particularly suitable for the formation of devices incorporating thermodynamically metastable alloys and has become a major process in the manufacture of optoelectronic devices such as Light-emitting diodes (LEDs).
The basic principle of MOCVD involves the injection of ultrapure precursor gases into a reactor, typically with a non-reactive carrier gas. These precursor gases consist of metalorganic species, which are usually liquid at room temperature, and other reactive gases. The metalorganic species serve as a source for one of the elements required for the growth of the thin film.
In MOCVD, ultrapure precursor gases are injected into a reactor, usually with a non-reactive carrier gas. These precursor gases can be metalorganic species, such as trimethyl gallium, which are usually liquid at room temperature. For example, in the growth of gallium arsenide, trimethyl gallium and arsine are commonly used as precursors.
As the precursor gases approach the semiconductor wafer, they undergo pyrolysis and the resulting subspecies absorb onto the wafer surface. Surface reactions then occur, leading to the incorporation of elements into a new epitaxial layer of the semiconductor crystal lattice. The growth of films in MOCVD is driven by supersaturation of chemical species in the vapor phase, and the process operates in a mass-transport-limited growth regime.
The growth of III-V semiconductors, such as gallium arsenide (GaAs) or indium phosphide (InP), can be achieved using various techniques, including metalorganic vapor-phase epitaxy (MOVPE) or metal-organic chemical vapor deposition (MOCVD).
In MOVPE/MOCVD, ultrapure precursor gases are injected into a reactor, usually with a non-reactive carrier gas. For III-V semiconductors, a metalorganic compound is used as the group III precursor and a hydride for the group V precursor. For example, trimethylindium ((CH3)3In) and phosphine (PH3) can be used as precursors for growing indium phosphide (InP).
As the precursors approach the semiconductor wafer, they undergo pyrolysis and the subspecies absorb onto the wafer surface. Surface reactions of the precursor subspecies result in the incorporation of elements into a new epitaxial layer of the semiconductor crystal lattice.
The growth of III-V semiconductors using MOVPE/MOCVD allows for the precise control of layer thickness, composition, and doping, making it suitable for the fabrication of complex semiconductor multilayer structures.
