Improvement of light extraction efficiency of GaN-based flip-chip LEDs by a double-sided spherical cap-shaped patterned sapphire substrate

This study reports on the development of a cost- and time-effective means to optimize a double-sided spherical cap-shaped patterned sapphire substrate (PSS) for highly efficient flip-chip GaN-based light-emitting diodes (LEDs). A simulation is conducted to study how light extraction efficiency (LEE) changed as a function of alteration in the parameters of the unit spherical cap for LEDs that are fabricated on a double-sided spherical cap-shaped PSS. Results show that the optimal double-sided spherical cap-shaped PSS can enhance LEE of flip-chip LEDs by over 5% compared with flip-chip LEDs grown on the optimal double-sided hemispherical PSS.