Identification of Deep Levels Associated with Extended and Point Defects in GeSn Epitaxial Layers Using DLTs

Gupta, Somya; Simoen, Eddy; Vrielinck, Henk; Merckling, Clément; Vincent, Benjamin; Gencarelli, Federica; Loo, Roger; Heyns, Marc

doi:10.1149/05301.0251ecst

Cited by 9 publications

(5 citation statements)

References 26 publications

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“…The H1 and H2 peaks at 130 and 160 K, respectively, visualized by using deconvoluted spectra (green lines) are due to bulk traps in the Ge buffer. 21 The peak response at 250 K is due to slow states (N bt ) and is not discussed in this work. The inset shows the shift in peak position as a function of period width T w .…”

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Density and Capture Cross-Section of Interface Traps in GeSnO₂ and GeO₂ Grown on Heteroepitaxial GeSn

Gupta

Simoen

Loo

et al. 2016

ACS Appl. Mater. Interfaces

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An imperative factor in adapting GeSn as the channel material in CMOS technology, is the gate-oxide stack. The performance of GeSn transistors is degraded due to the high density of traps at the oxide-semiconductor interface. Several oxide-gate stacks have been pursued, and a midgap Dit obtained using the ac conductance method, is found in literature. However, a detailed signature of oxide traps like capture cross-section, donor/acceptor behavior and profile in the bandgap, is not yet available. We investigate the transition region between stoichiometric insulators and strained GeSn epitaxially grown on virtual Ge substrates. Al2O3 is used as high-κ oxide and either Ge1-xSnxO2 or GeO2 as interfacial layer oxide. The interface trap density (Dit) profile in the lower half of the bandgap is measured using deep level transient spectroscopy, and the importance of this technique for small bandgap materials like GeSn, is explained. Our results provide evidence for two conclusions. First, an interface traps density of 1.7 × 10(13) cm(-2)eV(-1) close to the valence band edge (Ev + 0.024 eV) and a capture cross-section (σp) of 1.7 × 10(-18) cm(2) is revealed for GeSnO2. These traps are associated with donor states. Second, it is shown that interfacial layer passivation of GeSn using GeO2 reduces the Dit by 1 order of magnitude (2.6 × 10(12) cm(-2)eV(-1)), in comparison to GeSnO2. The results are cross-verified using conductance method and saturation photovoltage technique. The Dit difference is associated with the presence of oxidized (Sn(4+)) and elemental Sn in the interfacial layer oxide.

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“…The peak at 70K is due to D it . The H1 and H2 peaks at 130 and 160 K, respectively, visualized by using deconvoluted spectra (green lines) are due to bulk traps in the Ge buffer . The peak response at 250 K is due to slow states ( N bt ) and is not discussed in this work.…”

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confidence: 99%

Density and Capture Cross-Section of Interface Traps in GeSnO₂ and GeO₂ Grown on Heteroepitaxial GeSn

Gupta

Simoen

Loo

et al. 2016

ACS Appl. Mater. Interfaces

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“…17 Moreover, it has been reported that defects around the midgap (E V +0.29 eV) in Ge 1−x Sn x /Ge epitaxial layers appear to be associated with threading dislocations. 18 The physical origin and bez E-mail: wtakeuti@alice.xtal.nagoya-u.ac.jp havior of these hole-generating defects holes have not been clarified. One possible origin of the hole-generating defects is related to multivacancy complexes in the Ge matrix, which are known as acceptor-like states with an energy level of 10-20 meV above the valence band.…”

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Characterization of Shallow- and Deep-Level Defects in Undoped Ge₁₋_xSn_xEpitaxial Layers by Electrical Measurements

Takeuchi

Asano

Inuzuka

et al. 2015

ECS J. Solid State Sci. Technol.

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Shallow- and deep-level defects in undoped Ge1−xSnx epitaxial layers on Ge and Si grown by molecular beam epitaxy and metal–organic chemical vapor deposition were investigated by Hall effect, capacitance–voltage, and deep-level transient spectroscopy (DLTS) measurements. We discuss the effects of postdeposition annealing and introducing hydrogen during crystal growth on shallow-level defects in undoped Ge1−xSnx epitaxial layers. Using DLTS measurements, we found shallow- (

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“…A similar behavior, in which the buffer actively participates in the strain relaxation mechanism, has already been noticed for GeSn binaries grown at low temperatures on Ge‐VS in the same reactor . The absence of extended defects in the SiGeSn layer, such as threading dislocations or stacking faults, is especially beneficial for opto‐ and nanoelectronic applications, since, e.g., threading dislocations are known to form midgap trap states, thus seriously influencing device performance.…”

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confidence: 83%

SiGeSn Ternaries for Efficient Group IV Heterostructure Light Emitters

Driesch

Stange

Wirths

et al. 2017

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SiGeSn ternaries are grown on Ge‐buffered Si wafers incorporating Si or Sn contents of up to 15 at%. The ternaries exhibit layer thicknesses up to 600 nm, while maintaining a high crystalline quality. Tuning of stoichiometry and strain, as shown by means of absorption measurements, allows bandgap engineering in the short‐wave infrared range of up to about 2.6 µm. Temperature‐dependent photoluminescence experiments indicate ternaries near the indirect‐to‐direct bandgap transition, proving their potential for ternary‐based light emitters in the aforementioned optical range. The ternaries' layer relaxation is also monitored to explore their use as strain‐relaxed buffers, since they are of interest not only for light emitting diodes investigated in this paper but also for many other optoelectronic and electronic applications. In particular, the authors have epitaxially grown a GeSn/SiGeSn multiquantum well heterostructure, which employs SiGeSn as barrier material to efficiently confine carriers in GeSn wells. Strong room temperature light emission from fabricated light emitting diodes proves the high potential of this heterostructure approach.

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Identification of Deep Levels Associated with Extended and Point Defects in GeSn Epitaxial Layers Using DLTs

Cited by 9 publications

References 26 publications

Density and Capture Cross-Section of Interface Traps in GeSnO₂ and GeO₂ Grown on Heteroepitaxial GeSn

Density and Capture Cross-Section of Interface Traps in GeSnO₂ and GeO₂ Grown on Heteroepitaxial GeSn

Characterization of Shallow- and Deep-Level Defects in Undoped Ge₁₋_xSn_xEpitaxial Layers by Electrical Measurements

SiGeSn Ternaries for Efficient Group IV Heterostructure Light Emitters

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Identification of Deep Levels Associated with Extended and Point Defects in GeSn Epitaxial Layers Using DLTs

Cited by 9 publications

References 26 publications

Density and Capture Cross-Section of Interface Traps in GeSnO2 and GeO2 Grown on Heteroepitaxial GeSn

Density and Capture Cross-Section of Interface Traps in GeSnO2 and GeO2 Grown on Heteroepitaxial GeSn

Characterization of Shallow- and Deep-Level Defects in Undoped Ge1−xSnxEpitaxial Layers by Electrical Measurements

SiGeSn Ternaries for Efficient Group IV Heterostructure Light Emitters

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Density and Capture Cross-Section of Interface Traps in GeSnO₂ and GeO₂ Grown on Heteroepitaxial GeSn

Density and Capture Cross-Section of Interface Traps in GeSnO₂ and GeO₂ Grown on Heteroepitaxial GeSn

Characterization of Shallow- and Deep-Level Defects in Undoped Ge₁₋_xSn_xEpitaxial Layers by Electrical Measurements