Measurement of the excited-state position of bound-to-bound quantum-well infrared detectors

The energy of the first excited state of quantum-well infrared detectors plays an important role in determining performance. The uncertainties in material and growth parameters make it difficult to design quantum-well detectors with a precise control of the location of energy states. Such uncertainties will cause detectors to be either bound to continuum or bound to bound. In this article, we present a technique to locate the excited-state position in bound-to-bound quantum-well infrared detectors by measuring the bias dependence of the photoresponse. We have employed an InGaAs/AlGaAs quantum-well detector operating near 5 μm for this study. The photocurrent was found to have a strong bias dependence indicating the infrared transition in the quantum well is bound to bound in nature. The bias dependence of the photoresponse was compared with theoretical estimates including the tunneling of photoexcited electrons through the barrier. The results showed a good agreement and this allowed us to determine the location of the excited state from the barrier edge. copyright 2001 American Institute of Physics