A ZnSe/ZnSSe blue semiconductor laser was demonstrated to show very low threshold by direct photopumping of the ZnSe active layer. The lowest threshold at the excitation wavelength of 445 nm was 10 kW/cm2 at 300 K which is equivalent to the current density of 3.6 kA/cm2. This is the lowest threshold ever reported in II-VI photopumped lasers and is approaching the theoretically calculated threshold. The characteristic temperature of the threshold, which characterizes the temperature dependence of the threshold in the exponential form, was 124 K up to the measured 400 K and was comparable to III-V double-heterostructure lasers. The differential quantum efficiency remained the similar level up to 400 K and its decrease observed at 400 K was within 23% of the efficiency at 300 K.

A well-defined exciton absorption peak from a localized state was observed for the first time. The localized state was formed by fluctuation of well-barrier interfaces in a ZnSe/ZnSSe superlattice structure. Stimulated emission was observed from the localized state up to 100 K, and the physical origin is discussed from the temperature dependence of the stimulated emission peak. This opens the possibility to form a natural quantum box structure by controlling the well-barrier fluctuation.

Fundamental technologies for optical interconnection on a Si LSI chip have been developed using conventional silicon process technologies. The optical waveguides with SiO x N y core and SiO2 cladding layers and Al micromirrors to change the light propagation direction have been fabricated by low-temperature deposition. Moreover, the single test chip integrated with a light-emitting diode (LED), photodiode, waveguides and micromirrors has been fabricated and signal transfer between LED and the photodetector has been achieved.

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Correlation of room temperature photoluminescence to structural properties of ZnSSe/ZnSe superlattices grown by metalorganic vapor phase epitaxy ZnSe/ZnSSe superlattices (SLs) grown on GaAs substrates were studied with transmission electron microscopy and x-ray diffraction. Defects were observed in the initial growth stage, but they were recovered with the growth of short-period SL. The temperature dependent decrease of photoluminescence (PL) intensities improved in the short-period SL. Clear excitonic absorption peaks were observed in photocurrent spectra and the blue shift of the absorption peaks by the quantum confinement was in reasonable agreement with the calculated peak shift. In a SL with the well width of 93 A, a biexciton PL peak was observed from the very low excitation power of less than 1 mW/cm'. Details of the biexciton properties are discussed. ')Present address: