Continuous-Wave Magneto-Optical Determination of the Carrier Lifetime in Coherent Ge1−xSnx/Ge Heterostructures

Abstract

We present a magneto-optical study of the carrier dynamics in compressively strained Ge 1−x Sn x films with Sn content up to 10% epitaxially grown on Ge on Si(001) virtual substrates. We leverage the Hanle effect under steady-state excitation to study the spin-dependent optical transitions in the presence of an external magnetic field. This allows us to obtain direct access to the dynamics of the optically induced carrier population. Our approach reveals that at cryogenic temperatures the effective lifetime of the photogenerated carriers in coherent Ge 1−x Sn x is on the subnanosecond timescale. Supported by a model estimate of the radiative lifetime, our measurements indicate that carrier recombination is dominated by nonradiative processes. Our results thus provide central information to improve the fundamental understanding of carrier kinetics in this advanced direct-band-gap group-IV-material system. Such knowledge can be a stepping stone in the quest for the implementation of Ge 1−x Sn x -based functional devices.

High carrier lifetimes in epitaxial germanium–tin/Al(In)As heterostructures with variable tin compositions

“…Correspondingly, different measurement techniques, such as temperature dependent photoluminescence, microwave reflection and transmission probing, and non-contact PCD, were developed over the years. 44,45,48,49,53,54,61,62 In this work, the minority carrier recombination properties in Ge 1Ày Sn y /InAlAs and Ge 1Ày Sn y /GaAs or AlAs heterostructures were probed at 300 K using the ultrahigh frequency microwave reflection PCD analysis at the National Renewable Energy Laboratory (NREL). The Ge 1Ày Sn y minority carrier recombination properties were studied as a function of the Ge 1Ày Sn y epilayer thickness, surface roughness, and Sn alloy composition.…”

“…Carrier lifetimes in Ge 1Ày Sn y materials are expected to increase when grown on latticematched In x Al 1Àx As intermediate buffers, wherein defects and dislocations can be reduced to negligible levels, as opposed to the direct growth of Ge 1Ày Sn y on Si. [40][41][42][43][44][45][46][47][48][49] Lattice-matched Ge 1Ày Sn y /In x Al 1Àx As heterostructures can reduce the defect induced junction leakage and increase the carrier lifetime. Two design strategies are considered here to improve the Ge 1Ày Sn y material quality compared to the direct growth on Si: (a) the thickness of the Ge 1Ày Sn y epilayer on the AlAs/GaAs substrate below the critical layer thickness, and (b) the growth of the Ge 1Ày Sn y epilayer lattice matched to In x Al 1Àx As (no thickness constraints).…”

“…Carrier lifetimes in Ge 1− y Sn y materials are expected to increase when grown on lattice-matched In x Al 1− x As intermediate buffers, wherein defects and dislocations can be reduced to negligible levels, as opposed to the direct growth of Ge 1− y Sn y on Si. 40–49…”

Monolithic infrared silicon photonics: The rise of (Si)GeSn semiconductors

“…Since Sn incorporation depends on the growth temperature, with lower Sn content materials grown at higher temperatures, it appears likely that nonradiative lifetimes due to SRH recombination depend on the Sn content and worsen as the latter increases. 54 Another constraint in the design of GeSn/SiGeSn heterostructures is the higher growth temperature that is typically required for the SiGeSn cladding and barrier layers. In fact, low temperature Si incorporation is hindered by limited precursor (e.g., disilane)…”

Radiative Carrier Lifetime in Ge$_{1-x}$Sn$_x$ Mid-Infrared Emitters

“…For instance, timeresolved photoluminescence (PL) can hardly be applied to investigate materials at emission wavelengths in the mid-infrared range as high-speed detectors covering this range are not broadly available. Thus, the very few reported time-resolved studies concern Ge 1−x Sn x emitting below 2.3 µm corresponding to a relatively low Sn content * oussama.moutanabbir@polymtl.ca and/or highly compressively strained materials [19][20][21].…”