Molecular Beam Epitaxy of III-V Compounds: Technology and Growth Process

Molecular beam epitaxy (MBE) has now become a versatile technique for growing expitaxial thin films of semiconductors and metals by impinging thermal energy beams of atoms or molecules onto a heated substrate under ultra-high vacuum (UHV) conditions. Compared to the more established techniques of liquid phase epitaxy (LPE) and vapor phase epitaxy (VPE), the characteristic features of MBE are (a) the slow growth rate of 0.1-2.0 �m/hr that permits very precise control of layer thickness in the sub micron range; (b) the reduced growth temperature, e.g. 500600°C for GaAs, which is low enough not to disturb abrupt composi­ tional or doping profiles because of negligible bulk diffusion; ( c) the specific non equilibrium growth mechanism that is responsible for pro­ gressive smoothing of the surface for most substrate orientations; (d) the ability to abruptly cease or initiate molecular beams that produces hyperabrupt material interfaces and dopant profiles; and (e) the facility for in situ analysis to assure that the desired surface and reaction conditions are reached before commencement of growth and are main­ tained during crystal growth. Based on its potential for excellent dimensional control even over large lateral dimensions, the MBE process can uniquely tailor the electronic