Preparation and characterization of I-III-VI_2 chalcopyrite semiconductor superlattice by Metalorganic Molecular Beam Epitaxy.

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Epitaxial layrs of CuGaSe_2 and CuAlSe_2 and the CuGaSe_2/CuAlSe_2 superlattice have been grown by the metalorganic molecular beam epitaxy (MOMBE) and the molecular beam epitaxy (MBE).1. MOMBE The c-axis-oriented epitaxial layrs of CuGaSe_2 and CuAlSe_2 have been grown on the GaAs (100) substrate. Based on the X-ray diffraction photoluminescence (PL), the modulation reflectance and Raman methods, the epilayrs are found to be of good quality. The CuAlSe_2/CuGaSe_2/GaAs heterostructure and the superlattice of the layr thickness of 200A have been prepared. However, the XPS in-depth profile did not reflect the periodicity of the superlattice. This suggests that the flatness of the layr is not so good and the improvement of the surface morphology is required.2. MBE Epilayrs of CuGaSe_2 and CuAlSe_2 have been grown on the GaAs (100) substrate with the RHEED in situ measurement. The epilayrs with flat surface have been realized by trimming the Cu/III ratio and by decreasing the growth rate. T … More he CuAlSe_2/CuGaSe_2/CuAlSe_2/GaAs single quantum wells and the (CuAlSe_2/CuGaSe_2)_m superlattices have been prepared. PL measurements indicated that the alloyed layr of Cu (Al, Ga) Se_2 has been formed at the CuAlSe_2/CuGaSe_2 interface due to the interdiffusion of Ga and Al. Therefore, superlattices with layr thickness less than 200A are mostly alloyed at the growth temperature of 600C.The low growth temperature of 550C has proven to be useful in order to reduce the interdiffusion to realize superlattice formation.3. Band calculation of superlattice Energy band structures of CuAlSe_2/CuGaSe_2 and CuAlSe_2/ZnSe superlattices have been calculated by the semi-empirical tight-binding method. Increase of the bandgap energy has been found for the CuAlSe_2/CuGaSe_2 superlattice with layr thickness of less than 200A.Increase of the bandgap energy up to 250 meV has been found CuAlSe_2/ZnSe superlattice in which the both CuAlSe_2 and ZnSe have bandgap energy of 2.67 eV.The new band engineering for obtaining the large bandgap semiconductor has been suggested using the CuAlSe_2/ZnSe superlattice. Less