Effect of Diffusion-Barrier Insertion into the Reflector Electrode on QWIP Device Characteristics

摘要

We investigated GaAs/AlGaAs QWIP devices that had TiW/Au reflector electrodes and found that the thermal stability, and as a result, the uniformity of the IV characteristics were dramatically improved by the insertion of a TiW diffusion barrier. A secondary ion mass spectroscopy analysis showed that with the TiW insertion, the Au in-diffusion during the thermal process at around 400°C was completely suppressed. A reflectivity measurement of the GaAs/Au and GaAs/TiW/Au structures revealed that the reflectivities were almost the same, indicating the TiW/Au structure was a good candidate for use as a reflector electrode. A comparison of the fabricated GaAs/AlGaAs QWIP devices that had conventional Au with our new TiW/Au reflector electrodes showed that our devices exhibits a performance comparable with that of the conventional devices because of their similar reflectivity. Furthermore, the uniformity of the IV characteristics of more than 50 devices was greatly improved, especially in the reverse-biased region where the upper AlGaAs barrier (nearest to the reflector) served as an electron-emitter.