arXiv subjects

Md Samzid Bin Hafiz

Publications and source records attributed to Md Samzid Bin Hafiz.

2 recordsLinked to original sources

arXiv2026

Filamentary Transport and Thermoelectric Effects in Mushroom Phase Change Memory Cells

We performed a 2D finite-element electrothermal computational study of thermoelectric effects and filamentary electronic transport in Ge$_2$Sb$_2$Te$_5$ mushroom phase change memory cells during Reset and Set operations, accounting for spatial activation energy variations in amorphous Ge$_2$Sb$_2$Te$_5$ and phase-change dynamics. Reset operations with current going from the top electrode to the narrow 4 nm bottom electrode require $\sim$3x less energy and power, and $\sim$2x lower current to achieve the same Reset resistance, compared to the opposite polarity, due to thermoelectric effects. Filamentary conduction, electrical breakdown, thermal runaway, and local crystallization of amorphous Ge$_2$Sb$_2$Te$_5$ depend on current polarity and thermal boundary conditions, and determine the location, shape, and volume of the programming region, which may be significantly smaller than the semi-cylindrical mushroom region. The programming volume does not scale with contact dimensions larger than 10 nm. Larger contact areas introduce increased device-to-device and cycle-to-cycle variability due to filamentary conduction but are expected to lead to higher reliability and endurance.

physics.app-ph↗

arXiv2025

Modeling Filamentary Conduction in Reset Phase Change Memory Devices

We performed a computational analysis on percolation transport and filament formation in amorphous $Ge_2Sb_2Te_5$ (a-GST) using 2D finite-element multi-physics simulations with 2 nm out-of-plane depth using an electric-field and temperature dependent electronic transport model with carrier activation energies that vary locally around 0.3 eV and as a function of temperature. We observe the snapback (threshold switching) behavior in the current-voltage (I-V) characteristics at ~50 MV/m electric field with 0.63 $μ$A current for 300 K ambient temperature, where current collapses onto a single molten filament with ~ 2 nm diameter, aligned with the electric field, and the device switches from a high resistance state (108 $Ω$) to a low resistance state (103 $Ω$). Further increase in voltage across the device leads to widening of the molten filament. Snap-back current and electric field are strong functions of ambient temperature, ranging from ~ 0.53 $μ$A at 200 K to ~ 16.93 $μ$A at 800 K and ~ 85 MV/m at 150 K to 45 MV/m at 350 K, respectively. Snap-back electric-field decreases exponentially with increasing device length, converging to ~ 38 MV/m for devices longer than 200 nm.

physics.app-ph↗