On-chip light detection using integrated microdisk laser and photodetector bonded onto Si board

Characteristics of a compact III–V optocoupler heterogeneously integrated on a silicon substrate and formed by a 31 µm in diameter microdisk (MD) laser with a closely-spaced 50 µm × 200 µm waveguide photodetector are presented. Both optoelectronic devices were fabricated from the epitaxial heterostroctructures with InGaAs/GaAs quantum well-dot layers. The measured dark current density of the photodetector was as low as 2.1 µA cm−2. The maximum link efficiency determined as the ratio of the photodiode photocurrent increment to the increment of the microlaser bias current was 1%–1.4%. The developed heterogeneous integration of III–V devices to silicon boards by Au-Au thermocompression bonding is useful for avoiding the difficulties associated with III–V epitaxial growth on Si and facilitates integration of several devices with different active layers and waveguides. The application of MD lasers with their lateral light output is promising for simplifying requirements for optical loss at III–V/Si interface.

Увеличение оптической мощности микродисковых лазеров InGaAs/GaAs, перенесенных на кремниевую подложку методом термокомпрессии

The output power is studied under continuous-wave operation of microdisk lasers with InGaAs/GaAs quantum well-dots hybridly integrated with a silicon substrate with the epitaxial side down using the thermocompression bonding method. Owing a decrease in the thermal resistance and suppression of self-heating, an increase in the values of currents is observed at which the power is saturated and the lasing is quenched, as well as an increase in the peak power. In microdisks with a diameter of 19 µm, the highest output optical power in the continuous wave regime was 9.4 mW.

Atomic Study on Copper–Copper Bonding Using Nanoparticles

Thermocompression bonding of copper to copper using copper nanoparticles is studied using molecular dynamics. The bonding interface formation process is investigated frst. For the bonding process, the effects of temperature and external pressure are examined. Also, we examine the grain growth at the interface. The results show that the nanoparticles with high surface energy and low compressive strength provide the active atoms to bond with copper. Pressure determining the degree of deformation of nanoparticles transfers atoms from the interior to the surface of nanoparticles and provide more surface atom to form bonds with bulk copper. While continuous pressure increase does not help bonding, higher temperature will facilitate formation of vacancies by breaking the bonds and driving the metal atoms into these vacancies. In addition, a higher temperature promotes grain growth at the interface. These behaviors indicate that using nanoparticles as a bonding layer in metal bonding can effectively reduce bonding temperature and pressure. It is necessary to select appropriate pressure at initial bonding stage and provide continuous high-temperature hold time.