AlGaN-Based Light Emitting Diodes Using Self-Assembled GaN Quantum Dots for Ultraviolet Emission

摘要

Self-assembled GaN quantum dots (QDs) grown on Al_(0.5)Ga_(0.5)N have been used as the active region of light emitting diodes (LEDs). The LED emission wavelength exhibits a strong shift towards higher energies with increasing current density, which allows obtaining an emission in the UV range (down to 375 nm) above 100 A/cm~2. Together with this shift, a reduction of the electroluminescence (EL) peak full width at half maximum (FWHM) is observed. These features are a consequence of the quantum confined Stark effect caused by the built-in electric field in the heterostructure. At larger current densities, an opposite behavior (i.e., an increase of the FWHM) is observed concomitant with the appearance of an additional peak on the EL high energy side. This characteristic has been confronted with calculations and attributed to a transition between the lowest electron state and the first excited hole state in the QDs.