Optimization Of Underlying Layer And The Device Structure For Group-Iii-Nitride-Based Uv Emitters On Sapphire

Epitaxial lateral overgrowth. (ELO) was applied for the growth of AlGaN on a sapphire substrate by metalorgaic vapor phase epitaxy. Among several processes, the ELO of AlGaN on grooved AlGaN showed the best surface morphology and the lowest dark-spot density of 1 x 10(8) cm(-2) as measured using calthodoluminescence. The light output power of a UV LED fabricated on ELO-Al0.25Ga0.75N on grooved Al0.25Ga0.75N was the strongest among several UV LEDs fabricated by different processes. The effect of the Al composition in the electron-blocking (EB) layer an the performance of UV LEDs was investigated. The UV LED with a low-Al-content EB layer showed high output power under a low injection condition, while the output power of a UV LED with a high-Al-content EB layer did not saturate even under a high-inejection condition.