Deep UV light emitting diodes grown by gas source molecular beam epitaxy

We report the structural, electrical, and optical properties of deep UV light emitting diodes (LEDs) grown by gas source molecular beam epitaxy with ammonia on sapphire and AlN/sapphire template substrates. AlN/sapphire substrates were grown by stress controlled hydride vapor phase epitaxy (HVPE). LEDs based on n- and p-type AlN/Al x Ga 1−x N (0.05 ≤ x ≤ 0.08) superlattices are demonstrated operating to wavelengths as short as 250 nm. We report a significant enhancement in the cathodoluminescence intensities (by factor of ∼100) and photoluminescence lifetimes in the Al x Ga 1−x N/Al y Ga 1−y N superlattices consisting of well material grown in the three dimensional mode. We interpret these observations in terms of formation of quantum well/quantum dot active regions.