| 초록 |
To improve the electriacl and optical properties of InGaN/GaN multiple quantum well (MQW) light-emitting diodes (LEDs), a triangular-shape band structure was adopted for the active layer by grading In composition with growth time. Compared to the LEDs of conventional rectangular-shape QW structures, the triangular QW LEDs showed a higher intensity and a narrower linewidth of both photoluminescence (PL) and electronluminescence (EL) spectra, a lower operation voltage, and a stronger light-output power. Both PL and EL spectra of the triangular-QW-based LEDs also showed that the peak energy is nearly independent of the injection current and temperature, indicating that the triangular QW LED is more efficient and stable than rectangular one. Also, from plan-view transmission electron microscopy (TEM) images, the formation of uniformly distributed quantum dots (QDs) with small size and higher density was observed in triangular QW structures, suggesting that the QD engineering is attainable by changing the QW structure during the metalorganic chemical vapor deposition growth.
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