Low-temperature bonding technique for fabrication of high-power GaN-based blue vertical light-emitting diodes

Low-temperature Sn fusion bonding technique was proposed to fabricate GaN-based blue vertical lightemitting diodes (LEDs) on Si substrate. First, by studying photoluminescence (PL) spectra of GaN LED epilayers/ Ag-based mirror/Si structures fabricated at different bonding temperatures, it was confirmed that the quality of Ag-based mirror was not degraded when the bonding temperature was 250 °C. fabricated at this bonding temperature. As compared with conventional GaN-based LEDs, the vertical LEDs revealed improved forward current-voltage characteristic, especially, the reverse current of the vertical LEDs was as low as 39 nA at the reverse bias of -10 V. In the mean time, vertical LEDs showed an increase in light output of about 127% at 200 mA, and no saturation was observed as the driving current increased to 500 mA. Further measurement revealed that vertical LEDs had a much lower junction temperature. These results indicate that the Sn fusion bonding technique is an effective way for fabrication of high-power GaN-based LEDs.