ATOMIC LAYER EPITAXY OF III-V COMPOUNDS USING METALORGANIC AND HYDRIDE SOURCES

An overview of atomic layer epitaxy (ALE) for III-V compounds using metalorganic and hydride sources and its possibilities for device fabrication are described. Surface reactions involving the adsorption and desorption processes of source molecules play an important role in the self-limiting growth which is at the very heart of ALE. Various types of ALEs have been developed using metalorganic sources mainly for GaAs growth. Different models have been proposed to explain the self-limiting growth process. Homoepitaxial layers of GaAs, InP, GaP, InAs and lattice-matched ternary alloys all grow in a self-limiting manner. On the other hand, deviations were observed for some lattice-mismatched heteroepitaxial systems, arising from the large strain energy at the heterointerface and the exchange reactions between epitaxial layer atoms and substrate atoms. The growth of (GaAs)m(GaP)n strained-layered superlattices has demonstrated the large potential of ALE in superlattice growth, including monolayer superlattices. The reduction of carbon contamination, which was a serious issue in GaAs ALE, has been achieved and carrier concentrations ranging from 10(14) to 10(20) cm-3 for n-type GaAs and 10(15) to 10(21) cm-3 for p-type GaAs can now be obtained by control of growth conditions and doping levels. ALE offers unique possibilities for low-temperature growth, selective growth, side-wall growth and uniform-thickness growth. The ALE technique is now being applied to the growth of multilayers for high-speed and optoelectronic devices.