Abstract
Since the first demonstration of lasing in direct bandgap GeSn semiconductors, the research efforts for the realization of electrically pumped group IV lasers monolithically integrated on Si have significantly intensified. This led to epitaxial studies of GeSn/SiGeSn hetero- and nanostructures, where charge carrier confinement strongly improves the radiative emission properties. Based on recent experimental literature data, in this report we discuss the advantages of GeSn/SiGeSn multi quantum well and quantum dot structures, aiming to propose a roadmap for group IV epitaxy. Calculations based on 8-band k∙p and effective mass method have been performed to determine band discontinuities, the energy difference between Γ- and L-valley conduction band edges, and optical properties such as material gain and optical cross section. The effects of these parameters are systematically analyzed for an experimentally achievable range of Sn (10 to 20 at.%) and Si (1 to 10 at.%) contents, as well as strain values (−1 to 1%). We show that charge carriers can be efficiently confined in the active region of optical devices for experimentally acceptable Sn contents in both multi quantum well and quantum dot configurations.
Highlights
A significant outcome of technological development is the widespread use of network communications and data centers
The Si content range investigated in this work is limited to values of 10 at.%, which is realistic for SiGeSn layers grown by chemical vapor deposition (CVD)
This work presents the investigation of optimized material parameters for GeSn/SiGeSn heterostructures intended for use in efficient light emitting devices
Summary
A significant outcome of technological development is the widespread use of network communications and data centers. Since Sn has a negative bandgap at the Γ point, partial replacement of Ge by Sn atoms changes the electronic band structure of GeSn so that the Γ-valley energy EΓ decreases faster than the L-valley energy EL, increasing the directness ΔEL-Γ = EL − EΓ. This results in a transition into a fundamental direct bandgap semiconductor at Sn concentrations around 8 at.% for unstrained GeSn4,5. On the way towards an electrically pumped room temperature laser, GeSn research benefits from the previous development of III-V semiconductor lasers, where heterostructures have been introduced in the 60 s13 To pursue this approach, a suitable barrier material for GeSn has to be found.
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