An MOCVD Reactor in the Laboratory for Advanced Materials Synthesis
An MOCVD Reactor in the Laboratory for Advanced Materials Synthesis

Function
NRL's primary site for the exploration of crystal growth via metal-organic chemical vapor deposition (MOCVD). Current research activities include the growth of wide bandgap semiconductor materials and device structures for use in power electronics, RF communications, radar, and optoelectronics. Materials used in this activity are gallium nitride (GaN) and related alloys such as AlGaN and InGaN. Research activities range from basic research studies of materials and crystal growth to more applied investigations involving devices.

Description
The MOCVD growth of homoepitaxial or heteroepitaxial films of GaN, InGaN, and AlGaN is performed on lattice matched and mismatched substrates such GaN, SiC, sapphire, and silicon. The growth is accomplished by the reaction of metalorganic precursors that typically contain the column III metal, e.g., Ga(CH3)3 or Al(CH3)3, and the organometallic or hydride precursor of the column V element, e.g., NH3. Depending on the semiconductor being grown, the reactions take place at pressures 5% to 50% of ambient over a substrate heated in the range of 500º to 1100º C. Growth rates are typically determined by the column III precursor flux, which is controlled by the temperature and pressure of the sources and the mass flow rate of the high purity carrier gas flowing through the source, and range from 0.2 Å/s to 10 Å/s. The crystal quality is a direct function of growth parameters such as the pressure used for deposition. The epilayers can be doped n- or p-type with dopants such as Si or Mg. Through knowledge and control of the growth process, different types of structures containing complex heterojunctions can be grown. The equipment is housed in a specially designed and constructed building for the chemicals used in the growth process.

Instrumentation
The facility houses two state-of-the-art reactors for growth of GaN and its technologically important ternary compounds. Each reactor is equipped with in situ process monitoring equipment to aid in the growth of complex device structures. An additional reactor is reserved for gallium arsenide or indium phosphide growth and for growth of the technologically important ternary compounds of gallium arsenide. The laboratory has an integral safety system including gas detectors and alarms.