Development of Increased Reliability Vertical Cavity Surface Emitting Laser Arrays

: Vertical Cavity Surface Emitting Lasers (VCSELs) should see increasing use for short distance optical interconnects in the next 5-10 years: data rate requirements will exceed 10 Gbit/second. It was shown in the proposal that at these data rates electrical current requirements on the VCSELs cause excessive failure rates due to current mitigated defect formation and thermal rise in the active region. Here the thermal rise is addressed through reduction of thermal impedance from the active region to the heat sink. For 40 Gbit/second VCSELs, a reduction of thermal impedance from 1500 C/W to 100 C/W will increase mean lifetime from minutes to years. We proposed to achieve this reduction via flip-chip bonding of the VCSEL, using solder bonding directly to the VCSEL's active area, in conjunction with a reduction of the associated mirror stack via incorporation of metal reflectors. We have achieved 500 C/W, albeit with increased failure rate at a given active region temperature due to bond stresses. This quandary of being able to reduce thermal impedance by bonding near the active region to provide a direct heat path, but at the same time increasing failure rate at a given temperature because of the mechanical stresses induced needs to be addressed in future work.