Synthesis of Group-IV ternary and binary semiconductors using epitaxy of $\rm GeH_3Cl$ and $\rm SnH_4$

TL;DR

This study demonstrates the low-temperature epitaxial growth of Ge-Si-Sn alloys and binaries using a novel CVD source, achieving defect-free, strained films suitable for device applications, and explores growth behavior on different substrates.

Contribution

First demonstration of Ge-Si-Sn alloy growth using a new CVD source at ultra-low temperatures with high-quality microstructures.

Findings

Alloys grown at 160-200°C with uniform composition and defect-free microstructure.

Binary Ge-Sn films on Ge are fully strained with reduced Sn content.

Growth on Si results in relaxed films with challenges in maintaining homogeneity.

Abstract

$\rm{Ge}_{1-x-y}Si_{x}Sn_{y}$ alloys were grown on Ge buffer layers at ultra-low temperature using reactions of $\rm SnH_{4}$ and $\rm GeH_{3}Cl$ for the first time. The latter is a newly introduced CVD source designed for epitaxial development of group IV semiconductors under low thermal budgets and CMOS compatible conditions. The $\rm{Ge}_{1-x-y}Si_{x}Sn_{y}$ films were produced between 160-200oC with 3-5% Si and ~ 5-11 % Sn, which traverses the indirect to direct gap transition in Ge-Sn materials. The films were fully strained to Ge and exhibited defect-free microstructures, flat surfaces, homogeneous compositions, uniform thicknesses and sharp interfaces as required for device manufacturing. A comparative study was then conducted to investigate the applicability of $\rm GeH_{3}Cl$ for the synthesis of $\rm Ge_{1-y}Sn_{y}$ binaries under similar experimental conditions. The$\rm Ge_{1-y}Sn_{y}$ films were grown fully strained to Ge, but with reduced Sn compositions ranging from ~ 2 - 7 % and lower thicknesses relative to $\rm{Ge}_{1-x-y}Si_{x}Sn_{y}$. This prompted efforts to further investigate the growth behavior of $\rm Ge_{1-y}Sn_{y}$ using the $\rm GeH_{3}Cl$ method, bypassing the Ge buffer to produce samples directly on Si, with the aim of exploring how to manage interface strain. In this case the $\rm Ge_{1-y}Sn_{y}$ on Si films exhibited compositions and thicknesses comparable to $\rm Ge_{1-y}Sn_{y}$-on-Ge films; however, their strain states were mostly relaxed, presumably due to the large misfit between $\rm Ge_{1-y}Sn_{y}$ and Si. Efforts to increase the concentration and thickness of these samples resulted in non-homogeneous multi-phase materials containing large amounts of interstitial Sn impurities.