Ultra-violet nitride LED fabrication for high-flux white LED

摘要

The requirements for maximizing the external quantum efficiency of UV nitride LEDs are discussed. It is shown that as the chip wavelength progressively decreases, nitride epi growth on a sapphire substrate becomes advantageous in terms of light extraction. The epilayer requirements for UV LEDs dictate the growth of n-AlGaN, with increasing Al contents, and the growth of UV-transparent p-GaN. It is shown that MOCVD growth in a Emcore D-180 or Ganzilla reactor is ideal for meeting the stringent epilayer requirements. Increasing light extraction efficiency and wall-plug efficiency also requires optimization of the reflecting P-contact. The relative merits of Al- and Ag-based reflecting contacts are discussed. Performance data for UV LEDs on sapphire, for drive currents up to 700 mA is shown. Finally, a practical high power UV-based white lamp is demonstrated.