New strategies for Ge-on-Si materials and devices using non-conventional hydride chemistries: the tetragermane case

Abstract

We introduce a practical chemical vapor deposition strategy for next-generation Ge-on-Si epitaxy utilizing recently introduced Ge 4 H 10 hydride sources that confer unprecedented deposition efficiencies at very low-temperatures (<400 • C). The corresponding high growth rates produce thick bulk-like Ge films with structural and electrical properties significantly improved relative to state-of-the-art results obtained using conventional approaches. The use of a pure, single-source compound facilitates the control of residual doping, and enables p-i-n devices whose dark currents are not entirely determined by defects and whose zero-bias optical collection efficiencies are higher than obtained from samples fabricated using alternative Ge-on-Si approaches. The reaction pathways leading to the high-yield synthesis of Ge 4 H 10 are identified on the basis of quantum thermochemistry simulations. The results suggest a simple approach to routine synthesis of tetragermane as the main product in quantities sufficient to be deployed as a commercial source.

Frustrated incomplete donor ionization in ultra-low resistivity germanium films

“…The use of higher-order Ge-hydrides was motivated by the excellent quality of Ge layers grown recently at low temperatures with these compounds. 30 These low growth temperatures preserve the flat doping profiles characteristic of in situ doping, thereby reducing the uncertainties in the measurements of carrier and donor concentrations. Undoped buffer Ge layers with thicknesses between 600 nm and 2100 nm were grown by GSME on (001) Si wafers at substrate temperature near 350 C and pressure of 1.1 Â 10 À4 Torr using Ge 4 H 10 /H 2 mixtures.…”

Group IV Direct Band Gap Photonics: Methods, Challenges, and Opportunities

“…Frontiers in Materials | www.frontiersin.org (Vincent et al, 2011;Chen et al, 2013b;Wirths et al, 2013a;Xu et al, 2013;Du et al, 2014) for a variety of applications, e.g., photodiodes, photodetectors, or MOSFETs. Here, due to the reduced lattice mismatch compared to Si, Ge is preferred as virtual substrate (VS) in order to ensure layers of high monocrystalline quality.…”

Temperature dependence of the interband critical points of bulk Ge and strained Ge on Si

“…[31] We used tetragermane (Ge 4 H 10 ) as the precursor, diluted in hydrogen at a 1:20 ratio. Growth occurred at temperatures between 350 and 400 • C at a total pressure of 10 −4 Torr.…”

“…The full width at half maximum of the Ge (004) rocking curve is only 120". Additional information about these samples and their applications for photodiodes is given in [31].…”

“…[33,34] Determining the "growth temperature" T g in this simple model is not straightforward, since growth occurs in several steps at diferent temperatures followed by in situ annealing. [31] One might argue that the epilayer is anchored to the Si substrate during the initial stages of growth (near 650 K). One might also expect that the strain-free condition is reached at a higher temperature during the anneal step.…”