T. Tawara

Piezoelectric effects on photoluminescence properties in 10-nm-thick InGaN quantum wells

We report a large change in the photoluminescence (PL) properties induced by piezoelectric effects found in 10-nm-thick InGaN quantum wells. The time-resolved PL properties are measured with changing excitation intensity at 17 K. A blueshift in the PL peak of 200 meV and a decrease in the PL decay time from 3 μs to 17 ns are found with increasing excitation intensity. This large change is caused by a strong internal electric field up to 1 MV/cm and a spatial separation between an electron and a hole of as much as three times the Bohr radius.

Effects of nonradiative centers on localized excitons in InGaN quantum well structures

The authors report the effects of nonradiative recombination on the properties of spatially localized excitons in InGaN quantum well structures studied using a microphotoluminescence (PL) technique. Sharp PL lines (linewidth of less than 1meV) are clearly obtained by combining the PL and nanolithographic techniques. The PL originates from localized excitons induced by quantum-dot-like local potential minima where indium is accumulated. A systematic study with various kinds of samples reveals that suppressing the density of the nonradiative centers is crucially important in terms of observing the exciton localization effects rather than increasing the effects of indium accumulation.

Dispersion Relation of InGaN Cavity Polaritons Measured by Angle-Resolved Photoluminescence

Photoluminescence (PL) properties in a strong exciton-photon coupling regime are investigated using an InGaN quantum well microcavity. In angle-resolved PL measurements, we observe the dispersion of upper and lower polariton branches with Rabi splitting at room temperature.

Large piezoelectric effects on photoluminescence properties in 10 nm-thick InGaN quantum wells

The piezoelectric effects in InGaN quantum wells are examined using the time-resolved photoluminescence (PL) technique. An extremely large change in PL properties is found in a 10-nm thick quantum well with increasing excitation intensity.

Low-threshold lasing of optically pumped InGaN vertical-cavity surface-emitting lasers with dielectric mirrors

III-nitride VCSELs are fabricated by removing SiC substrate from the Ill-nitride cavity, and subsequent wafer bonding of the cavity and DBRs. Low-threshold lasing action in InGaN VCSELs with dielectric DBRs is observed at room temperature by optical pumping.

GaN-based blue laser diodes with deeply etched high-reflectivity DBR mirrors

A high mirror reflectivity of 62% is obtained for InGaN/GaN lasers using a deeply etched semiconductor/air DBR structure. The optimum design for the DBR mirrors with tilted sidewalls differs from the conventional /spl lambda//(4n) design.