STUDY ON INFRA-RED OPTICAL DEVICES BY Si_<1-x>Ge_x HETERO-STRUCTURES

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In this study, we have studied the fabrication technology of Si_<1-x>Ge_x/Si (100) hetero-structures and the charactersitics of Si_<1-x>Ge_x layrs in order to realize infra-red optical devices. Research results are as follows.1.By doping Sb impurities in MBE growth of Si_<1-x>Ge_x layrs, Ge segregation is suppressed and the strain-relaxation of Si_<1-x>Ge_x layrs is enhanced at the Ge fractions below 0.17. At x=1, however, strain-relaxation is suppressed. These results suggest that the strain-relaxation process is dominated by the increase in strain and the suppression of migration of Ge atoms by Sb atoms on the surface.2.The amount of doped Ga impurities in p-Si_<1-x>Ge_x layrs linealy increases as increasing the Ge fractions. Considering the adsorption and the segregation mechanism of Ga atoms in the growth, the adsorption and the incorporation rate of Ge atoms were estimated to be 2 and 40 times as large as Si atoms, respectively.3.TO-phonon-assisted bound exciton luminescence is observed at a temperature of 13K in heavily doped p-Si_<1-x>Ge_x/Si (100) systems. The bandgap of the p-Si_<1-x>Ge_x layrs is estimated by 1.124 and 1.092 eV for x=0.05 amd 0.1, respectively.4.Valence-band splittings of strained p-Si_<1-x>Ge_x layres were observed in measurements of magnetoresistance. The separation between the valence bands has a linear dependnce on the Ge fraction and the measurement temperature.5.Strain-relaxd Si_<1-x>Ge_x layres were grown by two-step growth method. By this method, atomic mixing at Si_<1-x>Ge_x/Si (100) interfaces is suppressed and the chemical compositions are well controlled, comparing with conventioanl method. Moreover, crystalline quality is also improved. It was also found that there is an optimum thickness of first layrs to minimize the surface roughness.