Superluminescent diode integrated with monitor photodiode

Ridge-waveguide superluminescent diodes with integrated rear-side monitoring photodiode have been fabricated. When electrical isolation trench is not etched to active layer, the leakage current of monitoring photodiode is determined by the resistance between active region electrode and monitoring photodiode electrode, i.e. the resistance multiplied by the leakage current approximately equals to 0.8 V. In order to reduce the leakage current of monitoring photodiode, the electrical isolation trench must be etched into substrate layer. In addition, the electrical isolation trench has to be far enough away from the active region so that the superluminescent diode could achieve small spectral ripple.