We investigated the structure of in-grown stacking faults in the 4H–SiC(0001) epilayers. The in-grown stacking faults nucleate near the substrate/epilayer interface and expand the area with increasing epilayer thickness in a triangular shape. From transmission electron microscope observation, the formation of 1c of 8H polytype was confirmed in the in-grown stacking fault area. We also investigated the dependence of in-grown stacking fault density on the epitaxial growth rate, growth temperature, and substrate surface preparation.

We demonstrate optically pumped telecom-band lasing in single InAs/InP nanowires at room temperature.

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The growth of Shockley type stacking faults in p-i-n diodes fabricated on the C-face of 4H-SiC during forward current operation was investigated using Berg-Barrett X-ray topography and photoluminescence imaging. After forward current experiment, Shockley type stacking faults were generated from very short portions of basal plane dislocations lower than the conversion points to threading edge dislocations in the epitaxial layer. The growth behavior of Shockley type stacking faults was discussed. Growth of stacking faults in the substrates was not observed.

We report the synthesis and optical properties of GaAs nanowires with very small diameters. We grew the GaAs nanowires by using size-selective gold particles with nominal diameters of 5, 10, 20, 40, and 60 nm. The diameter-controlled nanowires enable us to observe blueshifts of the free exitononic emission peak from individual nanowires with decreasing gold-particle size due to the two-dimensional radial quantum-confinement effect. We also analyze the absorption and emission polarization anisotropies of these bare GaAs quantum nanowires.

We investigated the dependency of minority carrier lifetimes on the nitrogen concentration, temperature, and the injected carrier concentration for highly nitrogen-doped 4H-SiC epilayers. The minority carrier lifetimes greatly shortened when the nitrogen concentration exceeded 1018 cm−3 through enhancing direct band-to-band and Auger recombination and showed a slight variation in the temperature range from room temperature (RT) to 250 °C. The epilayer with a nitrogen concentration of 9.3 × 1018 cm−3 exhibited a very short minority carrier lifetime of 38 ns at RT and 43 ns at 250 °C. The short minority carrier lifetimes of the highly nitrogen-doped epilayer were confirmed to maintain the values even after the subsequent annealing of 1700 °C. 4H-SiC PiN diodes were fabricated by depositing a highly nitrogen-doped epilayer as a “recombination enhancing layer” between an n− drift layer free from basal plane dislocations and the substrate. The PiN diodes showed no formation of stacking faults and no increase in forward voltage during current conduction of 600 A/cm2 (DC), demonstrating that a highly nitrogen-doped buffer layer with a short minority carrier lifetime successfully suppresses the “bipolar degradation” phenomenon.

Cavity polaritons are observed in InGaN quantum well (QW) microcavities at room temperature. High-quality microcavities are fabricated by the wafer-bonding of InGaN QW layers and dielectric distributed Bragg reflectors. The anticrossing behavior of strong exciton-photon coupling is confirmed by vacuum-field Rabi splitting obtained from reflection measurements. This strong coupling is also enhanced by increasing the integrated oscillator strength coupled to the cavity mode. The oscillator strength of InGaN QW excitons is 1 order of magnitude larger than that of GaAs QW excitons.

Telecommunication-wavelength quantum dots (QDs) were successfully grown by metalorganic vapor phase epitaxy using a novel growth method in which trimethylbismuth (TMBi) was supplied during the growth. Supplying TMBi during the growth was confirmed to have a surfactant effect, but did not result in the formation of a bismuth-containing alloy. Using this growth method, the photoluminescence intensity and wavelength of the QDs were much improved. It was found that the QD size was increased during the growth of the InGaAs covering layer; this effect partly resembled activated alloy phase separation reported for molecular-beam-epitaxy-grown QDs. For the realization of high density and multilayer QDs, we confirmed that a much higher V/III ratio than that of usual growth conditions and a strain-compensation structure are effective, respectively.