Water bonding of 50-mm-diameter mirror substrates to AlGaInP light-emitting diode wafers

The feasibility of bonding 50-mm-diameter Si with a Au/AuBe mirror to AlGaInP light-emitting diode (LED) wafers is demonstrated. Wafer bonding over the entire wafer area is achieved while the metallic mirror still maintains high reflectivity. Using this technique, the mirror-substrate AlGaInP LEDs are fabricated across an entire 50-mm wafer. The test data show that 98% of the dice with operating voltages <2.2 V at 20 mA and 85% of the dice with luminous intensity in the 130∼140 mcd region. The wafer-bonded mirror-substrate LED lamps operating at 626 nm can emit 3 lm at 20 mA with a forward voltage of 2 V, corresponding to a luminous efficiency of 74 lm/W. Moreover, they present a peak power efficiency of 21% with 4 mW output at 10 mA (1.9 V). Essentially no degradation is observed for these LEDs after 2000 h stress at 80°C and 50 mA (55.6 A/cm²). The results indicate the mirror-substrate AlGaInP LEDs of highly reliable and efficient performance.