Growth optimization for p-n junction placement in the integration of heterojunction bipolar transistors and quantum well modulators on InP

We demonstrate the necessary conditions for successful metalorganic vapor phase epitaxy (MOVPE) growth of InGaAs-InP-based heterojunction bipolar transistor (HBT) layers on p-i-n InGaAsP-InGaAsP quantum-well electroabsorption modulators. Optimization of the doping profile in the uppermost p-cladding layer of the modulator stack was achieved to obtain suitable p-n junction placement after the final HBT growth. Photoluminescence, electron beam induced current traces, scanning electron microscope photographs, and photocurrent spectra of etched diode mesa were utilized to study this process. In addition, the procedure described here will be useful in fine-tuning many other integration designs that include p-n junctions.