High mobility Si_0.15Ge_0.85 growth by using the molten target sputtering (MTS) within heteroepitaxy framework

Area of Science:

• Materials Science
• Semiconductor Physics

Background:

• Silicon-germanium (SiGe) films are crucial for next-generation photonics and electronics, offering superior performance over silicon-based devices.
• Conventional magnetron sputtering for SiGe heteroepitaxy requires high substrate temperatures (890°C), posing challenges for commercial manufacturing due to cost and time.

Purpose of the Study:

• To develop a cost-effective and robust method for growing high-mobility SiGe films at reduced substrate temperatures.
• To demonstrate the feasibility of Molten Target Sputtering (MTS) for practical SiGe device applications.

Main Methods:

• Utilized a novel Molten Target Sputtering (MTS) technique for SiGe film deposition.
• Grew Si_0.15Ge_0.85 films on sapphire substrates at a significantly reduced temperature of 500°C.
• Characterized film morphology, orientation, and electrical properties, including hall electron mobility and carrier concentration.

Main Results:

• Achieved continuous Si_0.15Ge_0.85 films with 99.7% majority orientation at 500°C using MTS.
• Obtained hall electron mobilities of 456 cm²V^-1s^-1 and 123.9 cm²V^-1s^-1 at carrier concentrations of 5.59×10¹⁸ cm^-3 and 3.5×10²⁰ cm^-3, respectively.
• Demonstrated a 550% increase in hall electron mobility compared to silicon at equivalent carrier concentrations and temperatures.

Conclusions:

• MTS is an economically viable and robust process for growing high-quality SiGe films at lower substrate temperatures.
• The developed MTS technique overcomes the limitations of high-temperature heteroepitaxy, making SiGe films more accessible for commercial device fabrication.
• MTS shows significant promise for heteroepitaxy frameworks involving materials with large lattice mismatches.