Wafer-scale all-epitaxial GeSn-on-insulator on Si(1 1 1) by molecular beam epitaxy

• Published in: Journal of physics. D, Applied physics Applied physics, 2018-08, Vol.51 (32), p.32
• Main Authors: Khiangte, Krista R, Rathore, Jaswant S, Schmidt, J, Osten, H J, Laha, A, Mahapatra, S
• Format: Article
• Language: English
• Subjects: epitaxy; gadolinium oxide; GeSn-on-insulator; group IV photonics
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/1361-6463/aad176

In this letter, fabrication of all-epitaxial GeSn-on-insulator (GeSnOI) heterostructures is investigated, wherein both the GeSn epilayer and the Gd2O3 insulator are grown on Si(1 1 1) substrates by conventional molecular beam epitaxy. Analysis of the crystal and surface quality by high-resolution x-ray diffraction, cross-sectional transmission electron microscopy, and atomic force microscopy reveals the formation of a continuous and fully-relaxed single-crystalline GeSn epilayer (with a root-mean-square surface roughness of 3.5 nm), albeit GeSn epitaxy on Gd2O3 initiates in the Volmer-Weber growth mode. The defect structure of the GeSn epilayers is dominated by stacking faults and reflection microtwins, which are formed during the coalescence of the initially-formed islands. The concentration and mobility of holes, introduced by un-intentional p-type doping of the GeSn epilayers, were estimated to cm−3 and cm−2 V−1 s−1, respectively. In metal-semiconductor-metal Schottky diodes, fabricated with these GeSnOI heterostructures, the dark current was observed to be lower by a decade, when compared to similar diodes fabricated with GeSn/Ge/Si(0 0 1) heterostructures. The results presented here are thus promising for the development of these engineered substrates for (opto-)electronic applications.