Analysis of Dark Current Mechanisms for Split-Off Band Infrared Detectors at High Temperatures

An analysis of dark current mechanisms has been performed on high-operating-temperature (up to 330 K) split-off (SO) band p⁺-GaAs/AlGaAs heterojunction infrared detectors (3-5 μm). In contrast to conventional 1-D current models due to carrier transport based on tunneling and/or thermionic emission mechanisms, a 2-D electrical model is used to explain nonuniformity degradation of zero-bias differential resistance (R_oA) with temperatures as measured on SO detectors. The 2-D characteristic of carrier transport could have the limitation on high-temperature performances of detectors and, hence, needs optimizing. A theoretical model shows that this 2-D effect can be reduced by structural modifications such as using smaller mesa sizes, higher doping of the p⁺ -GaAs layer, and a higher potential barrier that prospectively provides better electrical uniformity for SO detectors working at high temperatures.