Monolithic and hybrid near infrared detection and imaging based on poly-Ge photodiode arrays

In recent years, several Ge-on-Si technologies for the fabrication of near infrared photodetectors on Si substrates were proposed. In particular, using a low temperature (300 °C) technique, we have demonstrated poly-Ge_on_Si detectors with high speed and good NIR responsivity. The low process temperature allows the monolithic integration of the detectors as a final step in the fabrication of Si CMOS integrated circuits. After an introduction on poly-Ge, we describe a novel integrated chip (NIRCAM-1) designed as a readout/control circuit for arrays of 64 (32) poly-Ge_on_Si photodetectors. The photodiodes, monolithically integrated (wire-bonded with a hybrid approach) on the IC, generate a photocurrent which is then ADC converted after subtraction of the dark component, thus allowing a convenient digital readout of the array. The extensive optoelectronic characterization of the IC is presented.