Tensilely Strained Ge Films on Si Substrates Created by Physical Vapor Deposition of Solid Sources

Yize Stephanie Li,John Nguyen

doi:10.1038/s41598-018-35224-7

Yize Stephanie Li, John Nguyen

Open Access

https://doi.org/10.1038/s41598-018-35224-7

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Journal: Scientific Reports	Publication Date: Nov 13, 2018
Citations: 11	License type: open-access

Affiliation: California State University, Bakersfield

Abstract

The development of Si-compatible active photonic devices is a high priority in computer and modern electronics industry. Ge is compatible with Si and is a promising light emission material. Nearly all Ge-on-Si materials reported so far were grown using toxic precursor gases. Here we demonstrate the creation of Ge films on Si substrates through physical vapor deposition of toxin-free solid Ge sources. Structural characterization indicates that a high tensile strain is introduced in the Ge film during the deposition process. We attribute the presence of such a tensile strain to the difference in thermal expansion coefficient between Si and Ge. A Ge peak, centered at ~2100 nm, is evident in the photoluminescence spectra of these materials, which might result from direct band gap photoluminescence alone, or from superposition of direct band gap and indirect band gap photoluminescence. These Ge-on-Si materials are therefore promising in light emission applications.

Highlights

Ge, a Group IV semiconductor that is right below Si in the periodic table, is compatible with Si-based electronics
We created Ge films on native oxide- terminated or hydrofluoric (HF)- terminated Si(100) substrates, using solid Ge sources in a compact hot-wall chemical vapor deposition (CVD) system where Ar gas served as the carrier gas, as detailed in the Methods section
When the sample cools down naturally after the deposition, the substantial difference in thermal expansion coefficients between Ge and Si frustrates the shrinkage of Ge lattices, resulting in biaxial tensile strain in the Ge film

Summary

Introduction

A Group IV semiconductor that is right below Si in the periodic table, is compatible with Si-based electronics. This scenario, dispensing with the need for degenerate doping which results in absorption losses of free carriers and nonradiative recombination, is desirable for lasing and light emission applications. These Ge films exhibited direct band gap photoluminescence (PL), as expected for tensilely strained i-Ge films with a biaxial tensile strain value of 2% or higher, and are promising in lasing and light emission applications

Methods

Results

Conclusion