Ultra-Low-Temperature Epitaxy of Ge-based Semiconductors and Optoelectronic Structures on Si(100): Introducing Higher Order Germanes (Ge₃H₈, Ge₄H₁₀)

Abstract

This paper reports the development and optimization of an enhanced process to produce viable quantities of trigermane, and controlled smaller quantities tetragermane, which are isolated as a mixture of perfectly stable isomers. The identity and fundamental structural properties of these higher order germanes (Ge3H8, and Ge4H10 isomers) are thoroughly characterized using spectroscopic methods and quantum chemical simulations. These hydride products are found to exhibit a remarkably good stability and “ease of use”, making them compatible with current industry standards. As a proof-of-concept, we demonstrate that Ge3H8 and Ge4H10 both represent efficient and cost-effective precursors for ultra-low-temperature chemical vapor deposition of pure Ge and GeSn alloy films directly on Si(100) wafers, at conditions compatible with processes currently employed in next-generation group IV device designs. In the case of Ge the crystallinity of the resultant films is found of optical quality, in spite of the extremely low temperature processing, suggesting the potential for rapid adoption of the new processes into the device application arena. In the case of GeSn alloys, the high growth rates achieved at low temperatures (∼ 300 °C) allow the formation of highly concentrated bulk-like layers with unprecedented thicknesses compatible with Si-based photonic applications such as infrared (IR) emitters and detectors directly on Si wafers.

Controlled Growth of Dichlorogermanium Oligomers from Lewis Basic Hosts

“…[4,5] Drawn by this challenge and the uncertainty associated with the structures of the metastable halides (SiCl 2 ) n and (GeCl 2 ) n in the solid state, [6] we focused our efforts towards developing an efficient bottom-up synthesis of related oligomers and polymers (ECl 2 ) x (x ! [8] In pursuit of this goal, we herein report the mild and sequential synthesis of Lewis base supported germanium dichloride oligomers (GeCl 2 ) x (x ! This strategy is predicated on the propensity of strong electron-pair donors to bind/stabilize SiCl 2 and GeCl 2 in the form of stable molecular adducts LB·ECl 2 (E = Si and Ge).…”

“…Our efforts to install hydride functionality onto the Ge chain in 2 (to form germanium polyhydrides and/or clusters) [8,20] by treatment with Li[BH 4 ] led to the formation of IPr·GeH 2 ·BH 3 [10a] and germanium metal. The detailed mechanism of this transformation is unknown at this time, but our preliminary theoretical investigations (see below) suggest that isomerization of 2 to form related species, such as the linear isomer IPr·(GeCl 2 ) 4 , might be feasible.…”

“…Thermal ellipsoid plot (30 % probability level) of the [(IPrCH 2 ·GeCl 2 )3 Ge] 2+ dication in 4; selected hydrogen atoms, the [GeCl 3 ] À anions, and CH 2 Cl 2 solvate have been omitted for clarity. Selected bond lengths [] and angles[8]:…”

Band Gap-Engineered Group-IV Optoelectronic Semiconductors, Photodiodes and Prototype Photovoltaic Devices

“…13. We used 4 inch Ge(100) substrates with nominal thickness of 150-μm, miscut by 6 • toward (111) and doped p-type at levels of 6 × 10 17 cm −3 .…”

Tetragermacyclobutadiene: Energetically Disfavored with Respect to Its Structural Isomers

“…However, recent advances in the study of Ge hydrides that contain more than two Ge centers have suggested new possibilities for the development of Ge chemistry 27–30. In particular, Kouvetakis and co‐workers demonstrated the utility of trigermane (all‐Ge analogue of propane) and tetragermane (all‐Ge analogue of n ‐butane and isobutane) as precursors for semiconducting materials 28. Ge 4 H 4 not only serves as a computationally tractable model system for large molecules that contain Ge 4 motifs, but also deserves attention as a potential intermediate in synthetic procedures that employ larger Ge hydrides.…”