For LEDs with two top contacts, such as GaInN/GaN LEDs grown on sapphire substrates, both regular packaging (epi-side up) and flip-chip packaging is used. Flip-chip packaging using solder-bump bonding is a more expensive packaging process compared with regular packaging where the LED top contact pads are contacted by wire bonding. An advantage of flip-chip packaging of GaInN/GaN LEDs is that the metal pads are not hindering the extraction of light radiating from the active region.
In packaged epi-side up GaInN LEDs, a large-area p-type top contact that covers the entire p - type mesa results in a uniform current distribution in the active region. However, such a large top contact will hinder the extraction of light. This fundamental trade-off can be avoided by flip-chip packaging, which is especially advantageous for high-power devices.