Direct Bandgap Photoluminescence of GeSn grown on Si(100) substrate by Molecular Beam Epitaxy Growth

TL;DR

This paper reports the first observation of direct bandgap photoluminescence from MBE-grown GeSn layers on Si(100), demonstrating high-quality, Sn-rich GeSn with potential for optoelectronic applications.

Contribution

It presents the successful growth of high-quality, relaxed GeSn layers with high Sn content on Si(100) using MBE, and the first demonstration of direct bandgap PL from such films without post-growth annealing.

Findings

High Sn content GeSn layers (9.2% and 11.4%) were grown on Si(100).

Direct bandgap photoluminescence was observed at room temperature.

Structural analysis confirmed uniform Sn incorporation with minimal defects.

Abstract

Group IV alloys of GeSn have gained significant attention for electronic and optoelectronic applications on a Si platform due to their compatibility with existing CMOS technology, tunable band structure, and potential for a direct bandgap at high Sn concentrations. However, synthesizing Sn-rich GeSn structures remains challenging due to the low solid solubility of Sn in Ge (less than 1%) and the substantial lattice mismatch ( about 14%) between Sn and Ge. In this work, we demonstrate the successful growth of high-quality, relaxed GeSn layers with Sn contents of 9.2% and 11.4% on Si(100) substrates via molecular beam epitaxy (MBE). As far as we know, this is the first report of direct bandgap photoluminescence observed from MBE-grown GeSn films without post-growth annealing. Structural characterizations including X-ray diffraction (XRD), secondary ion mass spectrometry (SIMS), and transmission electron microscopy (TEM) confirm uniform Sn incorporation with minimal defect formation. Atomic force microscopy (AFM) reveals smooth surfaces with low roughness. Temperature-dependent photoluminescence (PL) measurements further confirm direct bandgap emission, representing a new stage in the development of MBE-grown GeSn.