By using wafer fusion techniques, two 5mm×5mm size lattice-mismatched single-crystal wafers of InP and GaAs are directly-bonded together. After chemical cleaning processes the two wafers are pressed against each other in a graphite sample holder at high temperature (470~700℃) in $H_2$ gas ambient.
Uniform bonding is realized and is confirmed by SEM photographs of cross-sectional bonding interface. The bonded wafer does not fall apart even after grinding and polishing processes. Therefore, this wafer fusion technique will be compatible with subsequent fabrication processes. The electrical property of the directly-bonded N-type wafer shows diode-like current-voltage characteristics, implying good electrical contact. The reflectivity of the directly-bonded oxide DBR shows no appreciable optical loss at the bonding interface. The photoluminescence characteristics of the bonded InGaAsP MQW shows slight shift in wavelength, depending on the substarte temperature.
