IR photoresponse characteristics of Mg2Ge pn-junction photodiodes fabricated by rapid thermal annealing

摘要

In this study, high purity n-type Mg2Ge single crystals are grown in graphite crucibles under nitrogen atmosphere using a facile growth process. X-ray diffraction proves that the grown crystal consists of only Mg2Ge single phase without any other additional impurity peaks. The clear symmetrical Laue diffraction pattern of the cleaved substrate demonstrates the single crystalline nature of the grown Mg2Ge crystal ingot. The Hall Effect measurement of the polished Mg2Ge wafer shows that the latter had a moderate carrier density (5.66 * 10(16) cm(-3)), mobility (253 cm(2)/V) and electrical resistivity (0.5 Omega. cm) at room temperature. Detailed analysis of the temperature dependence of the carrier density demonstrates that the shallow donor level, which gives rise to the n-type conduction of grown Mg2Ge crystals is due to the unintentional Al impurities from Mg source material. Mg2Ge pn-junction photodiodes are also manufactured for the first time by thermal diffusion of silver thin layer into n-Mg2Ge at 550 degrees C for 5 min in an argon atmosphere. The results reveal that the fabricated p-n photodiodes had a clear rectifying behavior and a remarkable spectral response in the wavelength range from 0.8 to 1.7 mu m with a maximum room temperature zero-biased photoresponse of 7mA/W at 1.2 mu m. These outcomes indicate that the fabricated Mg2Ge photodiodes are promising to detect short-wavelength infrared (SWIR) light in the above-mentioned wavelength domain. (C) 2019 Elsevier B.V. All rights reserved.