Red Shift In Photoluminescence Peak Position Research Articles

Temperature induced anomalous exciton localization in InGaN/GaN and GaN/AlInN quantum wells

This paper elucidates the details of exciton localization dynamics in InGaN/GaN and GaN/AlInN quantum wells (QWs) using Monte Carlo simulation for a wide range of temperatures (10---300 K). We find that the phonon-induced variation of exciton lifetimes has remarkable effects on the photoluminescence (PL) peak position and the line-width. The red-shift of PL peak position at high temperature is clarified. The combined effects of phonon-induced radiative lifetime of excitons and the band-gap shrinkage at high temperature show the most reasonable agreement with the experimentally observed red-shift of the PL peak position. We have also quantitatively explained the temperature dependence of the W-shaped line-width in both InGaN/GaN and GaN/AlInN QWs. These results are highly significant to understand the emission properties of III-nitride QWs optoelectronic devices.

Room-temperature band-edge photoluminescence from cadmium telluride.

Room-temperature photoluminescence (PL) spectroscopy of II-VI semiconductor alloys has been proposed as a useful tool for determination of spatial variations in alloy concentration and impurity concentration. However, the nature of the PL recombination can affect the emission peak energy, as well as line shape. These effects in the band-edge emission of the compound II-VI semiconductor CdTe are reported here. PL measurements at 300 K were recorded from (1) highly doped n-type CdTe films grown by molecular-beam epitaxy, (2) undoped high-resistivity (\ensuremath{\rho}\ensuremath{\sim}${10}^{8}$--${10}^{9}$ \ensuremath{\Omega} cm) bulk CdTe, and (3) as-grown nominally p-type (\ensuremath{\rho}\ensuremath{\sim}${10}^{4}$--${10}^{5}$ \ensuremath{\Omega} cm) bulk CdTe. The dependence of PL emission intensity and line shape over a range of excitation from 0.003--70 W/${\mathrm{cm}}^{2}$ was studied. As the excitation power density was increased, a redshift in PL peak position was observed from all samples. PL peak position, intensity, and line-shape analysis show the highly excitonic nature of the radiative recombination in these materials, even though the free-exciton binding energy in CdTe is about 1/3 of kT at 300 K. In addition, the PL peak position can be more than 7 meV higher from n-type CdTe as compared to undoped CdTe.