http://www.csmantech.org/Digests/2013/papers/032.pdf

INTRODUCTION Epitaxial growth of III-V materials is a cornerstone technology for the wireless, optical, and photovoltaic industries. Structures such as PHEMTs, HBTs, VCSELs, and multi-junction solar cells require the purity and crystalline quality that only epitaxial growth can provide. For III-V epitaxy, there are two technologies that are used in high volume, molecular beam epitaxy (MBE) and metalorganic vapor phase epitaxy (MOVPE). Within the epitaxial community there has always been debate over which technology is “better.” Before, attempting to elucidate the “better” question, it is necessary to provide a brief summary of each technique.

MBE

MBE is growth on a heated substrate in ultra-high vacuum (UHV) environment (base pressure ~1E-9 Torr) typically using elemental sources. The UHV environment not only ensures material purity, but it also results in highly directional elemental beams (no carrier gas required) due to the inherently long mean free paths. Layered structures are achieved by shuttering. In addition, valved sources are typically used for group V materials due to their relatively high vapor pressures. It is also possible to use compound decomposition sources (e.g., GaTe for Te doping), gas sources (e.g., CBr4 for C doping), and plasma sources (e.g., N plasma for nitride applications).

MOVPE (aka OMVPE or MOCVD)

MOVPE also grows on a heated substrate but in a much different pressure regime than MBE (typically 15 to 750 Torr). Rather than elemental sources, MOVPE uses more complex compound sources, namely metal-organic sources (e.g. tri-methyl Ga, In, Al, etc.), hydrides (e.g., AsH3, etc.), and other gas sources (e.g., disilane). In MOVPE, the reactants are flowed across the substrate where they react resulting in epitaxial growth. In contrast to MBE, MOVPE requires the use of a carrier gas (typically H) to transport reagent materials across the substrate surface. Layered structures are achieved by valve actuation for differing injection ports of a gas manifold.