(Invited) Engineering SiGeSn Semiconductors for MIR and THz Opto-electronic Devices

Abstract

Sn-containing group IV semiconductors (Si)GeSn represent a versatile platform to implement a variety of Si-compatible photonic, optoelectronic, and photovoltaic devices operating from SWIR to MIR wavelengths. This class of semiconductors provides two degrees of freedom, strain and composition, to tailor the band structure and lattice parameter thus enabling a variety of heterostructures and low-dimensional systems on a Si substrate.[1]In this presentation, the recent progress in the epitaxial growth and opto-electronic properties of metastable (Si)GeSn semiconductors with Sn contents above 15 at.% will be discussed. The growth of the (Si)GeSn multi-layer heterostructure is performed in a chemical vapor deposition (CVD) reactor on a Si wafer. By reducing the growth temperature, the Sn content in the alloy is increased, while preserving a high degree of crystal purity for the heterostructure in the topmost Sn-rich layer. Atom probe tomography (APT) measurements will be discussed to address the abruptness of the interfaces and the compositional profile across the GeSn multi-layer heterostructure.[2-4]By tailoring the strain relaxation in Ge0.83Sn0.17 room-temperature photoluminescence (PL) emission wavelength above 4.0 μm upon is achieved.[2,5] The absence of defect- and impurity-related emission and limited carrier losses into non-radiative recombination channels will be addressed using temperature-dependent PL measurements. Direct band gap absorption will be shown using transmission measurements performed at room-temperature, with energies closely matching the PL data. These observations will be discussed in the light of photocurrent measurements on GeSn photodetectors operating up to ~4.6 μm at room-temperature. The integration of p-i-n heterostructures in GeSn photodetectors will be investigated by correlating structural and opto-electronics properties of the fabricated devices.In addition, strategies to further extend the operational wavelength range of (Si)GeSn devices toward THz wavelengths will be discussed.[1] S. Wirths, et al., Prog. Cryst. Growth Charact. Mater. 62, 1 (2016)[2] S. Assali, et al., Appl. Phys. Lett. 112, 251903 (2018).[3] S. Assali, et al., J. Appl. Phys. 125, 025304 (2019).[4] S. Assali, et al., Appl. Phys. Lett. 114, 251907 (2019)[5] S. Assali, et al., arxiv:2004.13858