High-hole mobility polycrystalline Ge on an insulator formed by controlling precursor atomic density for solid-phase...

Area of Science:

• Materials Science
• Semiconductor Physics

Background:

• High-carrier mobility semiconductors on insulators are crucial for advanced thin-film transistors (TFTs), enabling 3D integrated circuits and high-performance mobile devices.
• Low-temperature fabrication methods are sought after to reduce costs and enable new device architectures.

Purpose of the Study:

• To investigate the effect of precursor deposition temperature on the solid-phase crystallization (SPC) of germanium (Ge) on glass substrates.
• To achieve high-carrier mobility in Ge thin films at low fabrication temperatures (<450°C).

Main Methods:

• Solid-phase crystallization (SPC) of Ge on glass substrates at temperatures ranging from 375-450°C.
• Systematic variation of substrate temperature during precursor deposition (T_d) from 50-200°C.
• Analysis of precursor atomic density and SPC properties to define distinct deposition regimes.

Main Results:

• Three precursor regimes were identified: low-density (T_d < 100°C), high-density (100°C ≤ T_d ≤ 125°C), and nucleation (T_d > 125°C).
• Utilizing the high-density regime resulted in SPC-Ge with a record hole mobility of 340 cm²/Vs.
• This high mobility is attributed to a large grain size (5 µm) and a low grain boundary energy barrier (6.4 meV).

Conclusions:

• Precursor conditions significantly influence the solid-phase crystallization of Ge on insulators.
• Optimized precursor deposition within a narrow high-density regime enables the fabrication of high-mobility Ge thin films at low temperatures.
• The understanding of precursor-crystallization relationships is broadly applicable to various materials for semiconductor applications.