Current conduction in quantum well infrared photodetectors under low bias operation

Device operation under low applied bias voltage has been examined for both p-type and n-type quantum well infrared photodetectors. Under low electric fields and at low temperatures, the carrier lifetime in the quantum well bound states is large compared to the intrawell carrier scattering time, allowing the carriers to thermalize in the heavily doped quantum wells. This thermalization process partially or fully decouples the statistical fluctuations in carrier transport through a barrier region from one section to the next. Therefore, the device can be thought of as M statistically independent sections in series, where M is equal to the ratio of active device length over the extended state carrier trajectory. Based on this concept and the additional assumption that the charge transport process is emission limited, the dark current was calculated for four different devices. The excellent agreement between the measured and calculated dark current–voltage characteristics confirms our model assumptions.