Monolithic integration of LD/HBTs on a semiinsulating InP substrate

A ridge-waveguide laser and heterojunction bipolar transistor were integrated monolithically on a semiinsulating InP. In this device, the n-cladding layer of the laser, the waveguide layer and the active layer were grown epitaxially on a semiinsulating InP. They are common to the collector and double-layer base of the transistor. Using this device structure, the step height on the device surface was small and the fabrication of the device was simplified. The threshold current of the laser was 30 mA and the characteristic temperature was 65 K. Since a narrowband gap layer common to the laser active layer exists at the collector side of the base of the heterojunction bipolar transistor, the saturation property of the current-voltage characteristic in common emitter configuration was good and influenced little by the “Early Effect.” This paper describes the fabrication and analysis of the ridge-waveguide laser and heterojunction bipolar transistor.