MOCVD processes are the most common application for palladium purifiers. For compound semiconductor processes, impurities will affect the electrical characteristics through compensation of dopants or unintentional doping, shift the intended emission wavelength in lasers or LEDs, and reduce device lifetime by degrading the interface and introducing imperfections in the crystal lattice. Epitaxy, in particular MOCVD, makes use of a variety of gases for growth and doping.
Hydrogen is the most prevalent gas because it is used as a carrier gas mixed with the specialty gases, and as a carrier gas for metalorganic (MO) precursors. Any impurities in the hydrogen may react with the MO, possibly contaminating cannisters of expensive precursors. Undesirable impurities could also be incorporated into the growing epilayer, leading to device failures.
Palladium technology is the preferred purifier because it removes all impurities including carbons and inerts, and it can remove the higher levels of oxygen that are common in compressed gas sources such as cylinders and tube trailers. Johnson Matthey palladium hydrogen purifiers have a theoretical infinite lifetime regardless of inlet impurity levels, so they can have much lower cost-of-ownership as compared to catalytic and getter purifier technology.
Typical Gases: Hydrogen, Nitrogen
Flow Rates: Hydrogen: 40 - 200 slpm Nitrogen: 5-50 slpm