Wafer-bonded bottom-emitting 850-nm VCSEL's on GaP substrates

Bottom-emitting 850-nm vertical-cavity surface-emitting lasers were fabricated using wafer bonding technology to replace the absorbing GaAs substrates with transparent GaP substrates. Ohmic-like p-type GaAs-GaP bonded interfaces were obtained with proper bonding condition. The devices with 4×4 μm
²
current aperture exhibit 24% external quantum efficiency, and threshold current as low as 400 μA. The threshold voltages range from 1.71 to 1.8 V for different aperture size devices.