Direct bonding of high quality InP on Si and its application to low threshold semiconductor lasers

High-quality InP layers were fabricated on Si by direct bonding at 700°C. Etch pit densities (EPDs) of the InP surfaces were significantly low, about 10⁴ cm^-2, the lowest values ever reported. The dislocation reduction mechanism was investigated by using TEM and by comparing three buffer layer structures on Si. The results indicated that the insertion of GaAs and GaP layers is important to relax the thermal stress and to reduce the propagation of threading dislocations in the buffer layer during the cooling stage (from ~10⁵ to ~10⁴ cm^-2). Furthermore,it was suggested that the dislocation density was reduced from ~10⁷ to ~10⁵ cm^-2 by the dislocation blocking effect of the (100) just/2" off misoriented bonded interface. The first low threshold RT pulsed operation of long-wavelength InGaAs/InGaAsP MQW mesa stripe lasers on Si substrates fabricated by direct bonding was demonstrated. The mesa stripe broad area lasers had a threshold current density of 1.7 kA/cm², which was comparable to the value for lasers on InP substrates