Tailoring the performances of low operating voltage InAlAs/InGaAs avalanche photodetectors.

We present tailoring of the performances of thin multiplication layer InAlAs/InGaAs avalanche photodetectors (APDs) with operating voltages lower than 20 V. Their operating voltages, gain-voltage slopes and dark currents were successfully tailored by changing the electric field distributions in avalanche region. The thin multiplication layer APDs show small activation energies of the dark current ranging from 0.12 to 0.19 eV at temperatures above 220 K, suggesting a band-trap-band tunneling dominant dark current mechanism over this temperature range. The dark currents show very weak temperature dependences at temperatures lower than 175 K, which mainly originate from the band-to-band tunneling and the surface leakage currents. The spectral responsivity of those APDs show anomalous negative temperature coefficients at gain factors larger than 1, which is attributed to the enhanced phonon scattering effect of carriers in the avalanche region at higher temperatures. Good gain factor uniformity at a given bias is observed for those APDs, and the charge layer is found to help improve the gain uniformity.