Near-IR detection by PbSGaAs heterojunctions

The properties of PbSGaAs p–n heterojunctions obtained by chemical deposition of PbS are reported. The photovoltage across the diode is produced by radiation in the wavelength range 0.9 to 3.2 μm, incident on the GaAs side, and is due to electron–hole pairs created at the interface and swept out by the junction field before recombination. The bandpass spectral responsivity depends on the temperature and relative doping levels of the two sides. In particular, flat bandpass detectors suitable for practical applications have been obtained. Electrical measurements indicate that the main conduction mechanism is the tunneling of carriers via localized states in the forbidden gap. To explain the experimental results, an energy band diagram different from that previously proposed for these heterojunctions has been introduced.