EXCESS TUNNEL CURRENTS IN ALGAAS/GAAS MULTIPLE QUANTUM-WELL INFRARED DETECTORS

We present experimental evidence of excess tunnel current at low temperatures in AlGaAs/GaAs multiple quantum well infrared detectors that is not accounted for by existing theory. Prior discussions of current mechanisms in these detectors only take into account ideal device properties. For quantum well detectors with thick barrier layers, which are useful for infrared detection, the excess tunnel current component possesses the features of sequential resonant tunneling, i.e., temperature independence of the current, and saturation of the current at intermediate bias voltages with negative conductance oscillations. However, the current is orders of magnitude larger than theory predicts. Comparison with data reported by other groups shows the magnitude of the discrepancy is sample dependent. These results suggest that defects play an important role in determining the tunnel current magnitude. This current component is significant because it limits attainable detector performance at low temperatures for applications requiring operation in reduced infrared backgrounds.