Integratable high linearity compact waveguide coupled tapered InGaAsP photodetectors

We investigate high linear response tapered photodiodes; composed of bulk and multiquantum-well absorption layers based on the integratable asymmetric twin waveguide architecture. The tapered shape reduces space-charge induced nonlinearities, enhancing the saturation current densities at high input optical powers. The 1-dB compression current density for an InGaAsP bulk active layer photodiode (BPD) is in excess of (2.8 +/- 0.3) kA/cm(2), compared to quantum-well photodiodes (QWPD) in the same materials system that saturate at (1.2 +/- 0.1) kA/cm(2). We find that the limited density of states of QWPDs leads to the early onset of current saturation. The BPD has a polarization sensitivity of S-Pol = (1.0 +/- 0.5) dB and responi sivity R = (0.3 +/- 0.03) A/W at a wavelength of 1.55 mu m, whereas the QWPD has S-Pol = (7 +/- 1) dB and R = (0.55 +/- 0.05) A/W, while both have a bandwidth of (11 +/- 1) GHz.