Growth, Electronic and Electrical Characterization of Ge-Rich Ge-Sb-Te Alloy

Area of Science:

• Materials Science
• Solid State Physics
• Electrical Engineering

Background:

• Ge-Sb-Te alloys are crucial for phase-change memory (PCM) applications.
• Optimizing alloy composition and deposition methods is key to improving device performance and thermal stability.
• Understanding the electronic and structural properties of amorphous Ge-rich alloys is essential for advanced memory technologies.

Purpose of the Study:

• To deposit and characterize a Ge-rich Ge-Sb-Te alloy (GST 29 20 28) for potential use in non-volatile memory.
• To investigate the electronic properties, composition, crystallization behavior, and electrical performance of the alloy.
• To evaluate the thermal stability and data retention capabilities of the fabricated memory cells.

Main Methods:

• Amorphous alloy deposition via physical vapor deposition (PVD) on silicon substrates.
• In-situ electronic property analysis using X-ray and ultraviolet photoemission spectroscopies (XPS and UPS).
• Structural characterization via Raman spectroscopy and X-ray diffraction (XRD) upon annealing.
• Electrical characterization of single memory cells, including I-V curves and SET/RESET performance.

Main Results:

• Successful deposition of amorphous Ge-rich Ge-Sb-Te alloy (GST 29 20 28) with confirmed composition.
• Crystallization studies revealed phase separation and segregation of crystalline Ge, with grain formation along the [111] direction.
• Electrical performance demonstrated alignment with conventional PVD-deposited (GeTe)n-(Sb2Te3)m alloys.
• Enhanced thermal stability observed, enabling data retention up to 230 °C.

Conclusions:

• The Ge-rich Ge-Sb-Te alloy exhibits promising properties for phase-change memory applications.
• The material offers competitive electrical characteristics combined with superior thermal stability compared to existing alloys.
• The enhanced data retention temperature suggests potential for next-generation high-density and reliable memory devices.