Distributed ARC Structure for Performance Optimization of Phase-Change Material-Based Tunable Photodetection

In the present work, an optimization of absorption for phase-change materials (PCMs) is proposed by arranging two anti-reflective coating (ARC) materials in distributed blocks within a single layer, i.e., in the same plane. PCMs such as Ge2Sb2Te5 generally exhibit two stable states known as amorphous and crystalline which can be interchanged through some suitable external stimuli. Both phases possess large contrast and noteworthy optical and electrical properties. While using germanium-antimony-tellurium (GST) material for photodetector device for possible tunable photodetection (by phase change), single ARC material is not sufficient for either phase as both phases are compatible to different ARC materials. One ARC could deteriorate the light-matter interaction properties of the system if the phase changes. Therefore, a distributed ARC structure of two ARC materials in a single layer/plane is proposed on a PCM layer (which is GST here) of the tunable photodetector device. Two ARC materials are determined by the two respective phases of the PCM material layer (which is just below the ARC plane) and finally placed in distributed blocks. The final chessboard-like structure is further optimized for optical-communication wavelength, i.e. 1550 nm. The absorption of the distributed structure area is a bit lower than the ARC materials corresponding to the respective phases of the PCM alone. However, the overall absorption is found to be improved, considering the tuning range of the PCM. The distributed ARC on a PCM surface that we propose may steer to a new passivation method of PCM with the best performance, specifically for tunable photodetection and photovoltaic applications.