We present electrical and optical properties of deep UV light emitting diodes (LEDs) based on digital alloys of AlN/Al 0.08Ga 0.92N grown by gas source molecular beam epitaxy with ammonia. Digital alloys are formed by growing short period superlattices consisting of AlN barriers, 0.75 nm to 2,00 nm thick, and Al 0.08Ga 0.92N wells, 0.50 nm to 1.25 nm thick. This allows us to vary the composition, up to the AlN content of 0.7, and the effective bandgap, up to 5.1 eV. Device structures consist of n- and p-type cladding layers based on digital alloys doped with Si derived from silane and Mg evaporated from an effusion cell, respectively, and an active region inserted between them. All the structures are grown on (0001) sapphire starting with a 50-nm thick AlN nucleation layer followed by a 1-micron thick Si-doped digital alloy layer transparent at wavelengths longer than 240 nm. This allows for light emission through the substrate. LEDs based on digital alloys operate in the range of 260 to 280 nm, exhibit turn-on voltages in the range of 4 to 6 V, and support room temperature dc current densities in excess of 500 A/cm 2.
|Number of pages||6|
|State||Published - Oct 28 2004|
|Event||State-of-the-Art Program on Compound Semiconductors XL (SOTAPOCS XL) and Narrow Bandgap Optoelectronic Materials and Devices II - Proceedings of the International Symposium - San Antonio, TX, United States|
Duration: May 9 2004 → May 14 2004
|Conference||State-of-the-Art Program on Compound Semiconductors XL (SOTAPOCS XL) and Narrow Bandgap Optoelectronic Materials and Devices II - Proceedings of the International Symposium|
|City||San Antonio, TX|
|Period||05/9/04 → 05/14/04|