We measured the thermal conductivity of amorphous silicon using a new simple steady state method implementing deposited Pt stripes as both resistive heaters and temperature monitors. Amorphous Si films were sputtered on Si substrates and heat was injected through the Pt resistive heaters. The increase in heater temperature was determined by the temperature-dependent electrical resistance of the Pt stripes. We thus determined the thermal conductivity of a-Si at room temperature to be 1.8 W/m·K, which is about one-hundredth of that of crystal Si. This information is very important to properly design the thermal resistance of long-wavelength surface emitting lasers which use the a-Si in high-reflective stack mirrors.

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We present studies of the interface abruptness of selectively oxidized AlAs/GaAs multilayer structures using transmission electron microscopy (TEM). High-resolution cross-sectional TEM images reveal that the interfaces between oxidized AlAs and unoxidized regions (GaAs and AlAs) are extremely abrupt on atomic scale. The widths of the transitional region are found to be within 4 monolayers for the interface between oxidized AlAs and unoxidized GaAs and 6.5 nm for the one between oxidized and unoxidized AlAs. The oxide layer thickness is found to decrease gradually from the oxidation front over a length of 200 nm.

Wafer bonding technology has been investigated to integrate InP lasers on Si wafers for optoelectronic integrated circuits. Room temperature continuous-wave (CW) operation of edge-emitting lasers and photo-pumped operation of surface-emitting lasers have been achieved. A novel bonding process which allows an integration of the optical devices on structured wafers, such as Si LSI wafers, has also been proposed. The wafer bonding is thought to be a promising technique to implement optical interconnections between Si LSI chips.

The electrical characteristics of directly bonded GaAs/InP heterointerfaces have been investigated for the first time. The mirror-polished surfaces of GaAs and InP wafers were put face to face and bonded by heat treatment at temperatures ranging from 450 to 700 °C. The wafers were successfully bonded without using any solders at all the temperatures tested. 1.3 μm InP/GaInAsP lasers were fabricated on GaAs substrates using direct bonding at 450 °C, and room-temperature lasing operation has been achieved with the threshold current identical to that of conventional InP lasers.