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This dissertation explores the synthesis and characterization of phosphine stabilized tetrel (group 14) cations. Tetrel cations are readily generated by reacting a halogermane or halostannane with a Lewis acid to generate an in situ germylium, stannylium cation or an in situ germyldiylium, stannyldiylium dication. A Lewis base such as a phosphine is added to the mixture to produce the corresponding salt with dative P-Sn or P-Ge connectivity. Tin and germanium salts represent new as well as unique cationic structures for phosphorus containing species. The preparation of these salts is proven to be generalizable, reproducible, and can be isolated as pure materials in moderate to high yields.

abstract: The work described in this thesis explores the synthesis of new semiconductors in the Si-Ge-Sn system for application in Si-photonics. Direct gap Ge1-ySny (y=0.12-0.16) alloys with enhanced light emission and absorption are pursued. Monocrystalline layers are grown on Si platforms via epitaxy-driven reactions between Sn- and Ge-hydrides using compositionally graded buffer layers that mitigate lattice mismatch between the epilayer and Si platforms. Prototype p-i-n structures are fabricated and are found to exhibit direct gap electroluminescence and tunable absorption edges between 2200 and 2700 nm indicating applications in LEDs and detectors. Additionally, a low pressure technique is described producing pseudomorphic Ge1-ySny alloys in the compositional range y=0.06-0.17. Synthesis of these materials is achieved at ultra-low temperatures resulting in nearly defect-free films that far exceed the critical thicknesses predicted by thermodynamic considerations, and provide a chemically driven route toward materials with properties typically associated with molecular beam epitaxy. Silicon incorporation into Ge1-ySny yields a new class of Ge1-x-ySixSny (y>x) ternary alloys using reactions between Ge3H8, Si4H10, and SnD4. These materials contain small amounts of Si (x=0.05-0.08) and Sn contents of y=0.1-0.15. Photoluminescence studies indicate an intensity enhancement relative to materials with lower Sn contents (y=0.05-0.09). These materials may serve as thermally robust alternatives to Ge1-ySny for mid-infrared (IR) optoelectronic applications. An extension of the above work is the discovery of a new class of Ge-like Group III-V-IV hybrids with compositions Ga(As1–xPx)Ge3 (x=0.01-0.90) and (GaP)yGe5–2y related to Ge1-x-ySixSny in structure and properties. These materials are prepared by chemical vapor deposition of reactive Ga-hydrides with P(GeH3)3 and As(GeH3)3 custom precursors as the sources of P, As, and Ge incorporating isolated GaAs and GaP donor-acceptor pairs into diamond-like Ge-based structures. Photoluminescence studies reveal bandgaps in the near-IR and large bowing of the optical behavior relative to linear interpolation of the III-V and Ge end members. Similar materials in the Al-Sb-B-P system are also prepared and characterized. The common theme of the above topics is the design and fabrication of new optoelectronic materials that can be fully compatible with Si-based technologies for expanding the optoelectronic capabilities of Ge into the mid-IR and beyond through compositional tuning of the diamond lattice. / Dissertation/Thesis / Doctoral Dissertation Chemistry 2018

abstract: Optoelectronic and microelectronic applications of germanium-based materials have received considerable research interest in recent years. A novel method for Ge on Si heteroepitaxy required for such applications was developed via molecular epitaxy of Ge5H12. Next, As(GeH3)3, As(SiH3)3, SbD3, S(GeH3)2 and S(SiH3)2 molecular sources were utilized in degenerate n-type doping of Ge. The epitaxial Ge films produced in this work incorporate donor atoms at concentrations above the thermodynamic equilibrium limits. The donors are nearly fully activated, and led to films with lowest resistivity values thus far reported. Band engineering of Ge was achieved by alloying with Sn. Epitaxy of the alloy layers was conducted on virtual Ge substrates, and made use of the germanium hydrides Ge2H6 and Ge3H8, and the Sn source SnD4. These films exhibit stronger emission than equivalent material deposited directly on Si, and the contributions from the direct and indirect edges can be separated. The indirect-direct crossover composition for Ge1-ySny alloys was determined by photoluminescence (PL). By n-type doping of the Ge1-ySny alloys via P(GeH3)3, P(SiH3)3 and As(SiH3)3, it was possible to enhance photoexcited emission by more than an order-of-magnitude. The above techniques for deposition of direct gap Ge1-ySny alloys and doping of Ge were combined with p-type doping methods for Ge1-ySny using B2H6 to fabricate pin heterostructure diodes with active layer compositions up to y=0.137. These represent the first direct gap light emitting diodes made from group IV materials. The effect of the single defected n-i¬ interface in a n-Ge/i-Ge1-ySny/p-Ge1-zSnz architecture on electroluminescence (EL) was studied. This led to lattice engineering of the n-type contact layer to produce diodes of n-Ge1-xSnx/i-Ge1-ySny/p-Ge1-zSnz architecture which are devoid of interface defects and therefore exhibit more efficient EL than the previous design. Finally, n-Ge1-ySny/p-Ge1-zSnz pn junction devices were synthesized with varying composition and doping parameters to investigate the effect of these properties on EL. / Dissertation/Thesis / Doctoral Dissertation Chemistry 2016

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Within the framework of this thesis, the influence of non equilibrium post growth thermal treatments of ion implanted and epitaxially grown Ge1-xSnx and Si1-x-yGeySnx layers for nano and optoelectronic devices has been investigated. The main focus has been placed on the study and development of thermal treatment conditions to improve the as grown layer quality and the fabrication of Ge1-xSnx and Si1-x-yGeySnx on SOI JNTs. In addition, through layer characterization, exhaustive analysis has provided deep insight into key material properties and the alloy´s response to the thermal treatment. For instance, (i) the conversion of as grown in plane compressive strained Ge1-xSnx into in-plane tensile strained Ge1-xSnx after PLA that is required for high mobility n-type transistors and (ii) the evolution of monovacancies to larger vacancy clusters due to post growth thermal treatments. Moreover, the adaption of CMOS compatible fabrication approaches to the novel Ge1-xSnx and Si1-x-yGeySnx alloys allowed the successful fabrication of first lateral n-type JNTs on SOI with remarkable Ion/Ioff ratios of up to 10^8 to benchmark the alloy performance.:I. Table of contents II. Abstract III. Kurzfassung (Abstract in German) IV. List of Abbreviations V. List of Symbols VI. List of Figures VII. List of Tables 1 Introduction 2 Fabrication and properties of Ge1 xSnx and Si1 x yGeySnx alloys 2.1 Alloy formation 2.2 Strain and defects 2.3 Electrical and optical properties 2.3.1 Band structure of strain relaxed alloys 2.3.2 Band structure of strained alloys 2.3.3 Doping influenced properties 2.3.4 Electrical properties 2.4 Thermal treatments 2.4.1 Rapid thermal annealing 2.4.2 Flash lamp annealing 2.4.3 Pulsed laser annealing 2.5 Summary 3 Experimental setups 3.1 Molecular beam epitaxy (MBE) 3.2 Ion beam implantation 3.3 Pulsed laser annealing (PLA) 3.4 Flash lamp annealing (FLA) 3.5 Micro Raman spectroscopy 3.6 Rutherford backscattering spectrometry (RBS) 3.7 X ray diffraction (XRD) 3.8 Secondary ion mass spectrometry (SIMS) 3.9 Hall effect measurement 3.10 Transmission electron microscopy (TEM) 3.11 Positron annihilation spectroscopy (PAS) 3.12 Cleanroom 4 Post growth thermal treatments of Ge1-xSnx alloys 4.1 Post growth pulsed laser annealing 4.1.1 Material fabrication and PLA annealing 4.1.2 Microstructural investigation 4.1.3 Strain relaxation and optical properties 4.1.4 Electrical properties and defect analysis 4.1.5 Strain relaxed Ge1-xSnx as virtual substrates 4.1.6 Conclusion 4.2 Post growth flash lamp annealing 4.2.1 Material fabrication and r FLA annealing 4.2.2 Alloy composition and strain analysis 4.2.3 Defect investigation 4.2.4 Dopant distribution and activation 4.2.5 Conclusion 5 Fabrication of Ge1-xSnx and Si1-x-yGeySnx alloys on SOI 5.1 Alloy fabrication with ion beam implantation and FLA 5.1.1 Si1-x-yGeySnx formation via implantation and FLA 5.1.2 Si1-x-yGeySnx on SOI fabrication via implantation and FLA 5.1.3 Recrystallization of Si1-x-yGeySnx on SOI by FLA 5.1.4 P and Ga doping of Si1 x yGeySnxOI via implantation and FLA 5.1.5 Conclusion 5.2 MBE and post growth thermal treatments of Ge1-xSnx and Si1-x-yGeySnx on SOI 5.2.1 MBE growth of Ge0.94Sn0.06 and Si0.14Ge0.80Sn0.06 on SOI 5.2.2 Microstructure of as grown Ge0.94Sn0.06 and Si0.14Ge0.80Sn0.06 5.2.3 Microstructure after post growth thermal treatments 5.2.4 Dopant concentration and distribution 5.2.5 Conclusion 6 Ge1-xSnx and Si1-x-yGeySnx on SOI junctionless transistors 6.1 Operation principle of n type JLFETs 6.2 Fabrication of n-type JNTs 6.3 Electrical characterization 6.3.1 JNT performance evolution during processing 6.3.2 JNT performance in dependence on post growth PLA 6.3.3 Gate configuration of Ge1-xSnx JNTs 6.3.4 Influence of post fabrication FLA on Ge1-xSnx JNTs 6.4 Conclusion 7 Conclusion and future prospects References 8 Appendix 8.1 Sample list and fabrication details for Chapter 4 8.2 Extended RBS information 8.3 Extended TEM analysis for section 4.1.2 8.4 Strain calculation based on (224) RSM 8.5 Strain calculation by µ Raman 8.6 Analysis of Hall effect measurements 8.7 VEPFit and ATSUP simulations 8.8 Strain relaxation of Ge0.89Sn0.11 for section 4.1.5 8.9 COMSOL simulation of FLA temperature 8.10 ECV measurement setup 8.11 Datasheet of the SOI wafers 8.12 Sample list of Chapter 5 8.13 Calculation of the ion beam implantation parameter by SRIM 8.14 RBS simulation results for section 5.1 8.15 GI XRD and (224) XRD RSM results for section 5.1 8.16 SIMS limitations for section 5.1.4 8.17 RBS of Ge1-xSnx on SOI for section 5.2.3 8.18 Fit procedure for SOI RSM peak positions 8.19 Supporting µ Raman results for section 5.2.3 8.20 Process details for n-JNT fabrication 8.21 Flat band voltage VFB and on current Ion of JNTs 8.22 Ioff, Imax, Ion/Ioff and Imax/Ioff ratio of JNTs 8.23 Subthreshold swing SS calculation of JNTs 8.24 Threshold voltage Vth of JNTs 187 8.25 Gate configuration of Si1-x-yGeySnx JNTs 8.26 n-type transistors compared in Chapter 7 8.27 Annealing setup description

L’alliage germanium-étain est un semiconducteur qui suscite une grande attention en raison de ses propriétés électriques et optiques. L’incorporation de Sn dans le germanium permet d’ajuster la largeur de bande interdite (gap) et d’améliorer la mobilité des électrons et des trous, et pour une quantité suffisante d’étain, le matériau passe d’un gap indirect à direct. Cet alliage est versatile parce qu’il peut être intégré d’une façon monolithique sur le Si, c’est ce qui en fait un matériau idéal dans les domaines de l'optoélectronique à base de silicium. Cette thèse est sur la fabrication et la caractérisation de nanofils cristallins Ge1-xSnx à haute concentration en Sn. Des nouvelles stratégies ont été employées pour fabriquer de nombreux types de nanofils GeSn. Les résultats ont été expliqués en fonction des modèles cinétiques existants. Un nouveau mécanisme de croissance y est décrit: le mécanisme solide-solide-solide – SSS. Il consiste à faire croître des nanofils de GeSn dans le plan du substrat à l’aide de catalyseurs d’étain à une température inférieure au point de fusion de Sn. Quatre modèles de transport de masse sont proposés pour le mécanisme de croissance du SSS. Diverses caractérisations (par exemple TEM et APT) ont été effectuées pour étudier les propriétés physiques, et chimiques des nanofils. / Germanium-Tin alloy is a unique class semiconductor gaining a strong attention because of its significant electrical and optical properties. Sn incorporation in Ge allows straightforward band-gap engineering enabling to enhance the electron and hole mobilities, and for a sufficient Sn amount an indirect-to-direct band-gap transition occurs. Its versatility rises due the possible monolithic integration on Si-platforms making it an ideal material in domains of optoelectronics, and high speed electronic devices. This thesis has focused on the fabrication and characterization of crystalline Ge1-xSnx nanowires with high Sn concentrations. New strategies were designed to fabricate many types of GeSn nanowires. The results have been explained as function of the existing kinetic models. A new growth mechanism was reported (i.e. Solid-Solid-Solid mechanism – SSS), it consists of growing in-plane GeSn nanowires using Sn catalysts below the melting point of Sn. Four mass transport models were proposed for the SSS growth mechanism. Various characterizations (e.g. TEM and APT) were done to investigate the physical and chemical properties of the obtained nanowires.