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

Bottom-emitting 850-nm vertical-cavity surface-emitting lasers were fabrica ted using wafer bonding technology to replace the absorbing GaAs substrates with transparent Gap substrates, Ohmic-like p-type GaAs-GaP bonded interfa ces were obtained with proper bonding condition. The devices with 4 x 4 mu m(2) current aperture exhibit 24% external quantum efficiency, and threshol d current as low as 400 mu A. The threshold voltages range from 1.71 to 1.8 V for different aperture size devices.