Chemical Beam Epitaxy of Chalcopyrite Semiconductors

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We have investigated the growth of chalcopyrite materials, AgGaS_2 AND AgGaSe_2, which have potential for light-emitting devices and nonlinear potics on GaAs (001) substrates by using chemical beam epitaxy. The major results obtained are as follows.1. AgGaS_2 epitaxial films have been successfully grown on GaAs (100) substrate oriented c-axis normal to the substrate surface by using elemental silver, trimethylgallium, and hydrogen sulfide as source materials, for the first time2. in-situ observation by reflection high enegy electron diffraction (RHEED) measurements reveal the initial nucleation mechanism from island growth to layr-by-layr growth, which is indicated by the streaked RHEED pattern, and rapid lattice relaxation.3. It is found that the deposition of AgGaS_2 has been obtained only at very limited substrate temperature range of 600-630 ﾟC,and excess sulfur beams reduce the growth rate and crystalline quality.4. A AgGaS_2 epitaxial layr grown at optimized condition has shown band-edge photoluminescence emission at low temperature, which demonstrate good crystalline quality of the epitaxial layr.5. AgGaSe_2 layrs oriented a-axis normal to the substrate have been grown on GaAa (100) substrates by using all elemental sources of silver, gallium, and selenium.