No abstract

The integration of III–V active devices on a Si platform utilizing direct bonding is an attractive way to realize large-scale photonic integrated circuits. Because plasma activated bonding (PAB) is expected to have a higher bonding strength at a lower heating temperature as compared to conventional bonding methods, PAB is attractive for the reduction of non-radiative recombination centers in the III–V active region caused by thermal expansion during the bonding process. A GaInAsP/Si hybrid laser was fabricated with low-temperature (150 °C) N2 PAB, and a low threshold current density of 850 A/cm2 (170 A/cm2 per quantum well) was obtained.

We fabricated a novel lateral-current-injection-type distributed feedback (DFB) laser with amorphous-Si (a-Si) surface grating as a step to realize membrane lasers. This laser consists of a thin GaInAsP core layer grown on a semi-insulating InP substrate and a 30-nm-thick a-Si surface layer for DFB grating. Under a room-temperature continuous-wave condition, a low threshold current of 7.0 mA and high efficiency of 43% from the front facet were obtained for a 2.0-μm stripe width and 300-μm cavity length. A small-signal modulation bandwidth of 4.8 GHz was obtained at a bias current of 30 mA.

Toward the light source for on-chip interconnection, a current-injection-type membrane distributed feedback laser with a surface gating structure is demonstrated. In this device, 450-nm-thick GaInAsP/InP layers with lateral-current-injection structure prepared by a two step OMVPE regrowth-method is bonded on a host substrate by using Benzocyclobutene bonding process. A threshold current of I th =11 mA is obtained with a cavity length of 300 µm and a stripe of 1 µm.

A low-temperature direct wafer bonding technique has been researched by using plasma treatment. Si-to-Si direct bonding strength was 1.6 MPa by using plasma pretreatment prior to the heating and weighting. 1.4 MPa of InP/Si bonding strength was obtained by improving chemical cleaning process. On the other hand, photoluminescence properties of GaInAs/InP quantum wells bonded on Si substrate were investigated. An introduction of a 30-nm-thick superlattice buffer on the top of the wafer greatly suppressed photoluminescence intensity degradation near the bonded interface.