Methods and Compositions for Preparing Tensile Strained Ge on Ge1-ySNy Buffered Semiconductor Substrates

Abstract

The present disclosure describes methods for preparing semiconductor structures, comprising forming a Ge1-ySny buffer layer on a semiconductor substrate and forming a tensile strained Ge layer on the Ge1-ySny buffer layer using an admixture of (GeH3)2CH2 and Ge2H6 in a ratio of between 1:10 and 1:30. The disclosure further provides semiconductor structures having highly strained Ge epilayers (e.g., between about 0.15% and 0.45%) as well as compositions comprising an admixture of (GeH3)2CH2 and Ge2H6 in a ratio of between about 1:10 and 1:30. The methods herein provide, and the semiconductor structure provide, Ge epilayers having high strain levels which can be useful in semiconductor devices for example, in optical fiber communications devices.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a Divisional of U.S. patent application Ser. No. 12 / 133,221, filed Jun. 4, 2008 which claims the benefit under 35 USC §119(e), of U.S. Provisional Application Ser. No. 60 / 933,013, filed 4 Jun. 2007, which is hereby incorporated by reference in its entirety.STATEMENT OF GOVERNMENT INTEREST[0002]The invention described herein was made in part with government support under grant number FA9550-06-01-0442, awarded by AFOSR under the MURI; and under grant number DMR-0526734, awarded by the National Science Foundation. The United States Government has certain rights in the invention.BACKGROUND OF THE INVENTION[0003]Germanium has a direct band gap E0=0.81 eV at room temperature (see, MacFarlane and Roberts, Phys. Rev. 97, 1714 (1955)), which corresponds to an optical wavelength of 1.54 μm. Although this is barely enough to reach the telecom C-band (1.53 μm-1.56 μm), the very strong wavelength dependence of the absorption coeff...

AI Technical Summary

Benefits of technology

[0013]Herein is provided an approach based for the generation of tensile-strained Ge epilayers based on the creation of Ge1-ySny alloys with tunable lattice dimensions above that of Ge which serve as the critical facilitating platforms for the subsequent tensile-Ge growth. In addition this approach subsumes the following distinctive features: (i) low growth temperature that promotes the assembly of highly-strained tetragonally-distorted Ge structures that remain robust despite the inherent metastability. (ii) layer-by-layer growth mechanisms leading to flat surfaces, chemically abrupt interfaces devoid of chemical intermixing and relatively defect free layer microstructures. Both features are enabled by exploiting the high reactivity and the pseudo-surfactant behavior of the (GeH3)2CH2 species. Collectively this methodology has allowed the systematic production of Ge layers with very high tensile strains and all of the desired morphological and structural properties as discussed below. Thereby, the utility of Ge can be extended into the wider infrared optoelectronic domain by tuning its fundamental optical properties using strain as a main parameter

Problems solved by technology

The use of stress as a perturbation is problematic because the direct band gap can only be lowered with tensile strain.

Further limitations of the thermal expansion process include lack of precise strain control and a maximum predicted strain value of 0.3% for growth at 900° C.

Moreover, the use of high temperatures (800-900° C.) typically induces inter-diffusion of the elements across the Si—Ge heterojunction, resulting in non-uniform and potentially defective interfaces.

In the context of laser applications, spatial confinement requires abrupt interfaces, which are precluded using this high temperature process due to the inherent elemental intermixing at the interface.

In addition, precise and systematic control of the final strain state has not been demonstrated using this method, and this hampers the design of devices.

Images