Charge Retention in Quantized Energy Levels of Nanocrystals

TL;DR

This paper investigates charge retention in germanium nanocrystals embedded in silicon oxide, using capacitance spectroscopy and a tunnelling-based model to understand discharge dynamics and optimize nanocrystal memory devices.

Contribution

It introduces a theoretical model for charge decay in nanocrystals based on quantized energy levels and validates it with experimental data.

Findings

Charge is stored in quantized energy levels of nanocrystals.

Discharge rates match the tunnelling-based decay model.

Experimental results confirm the model's accuracy.

Abstract

Understanding charging mechanisms and charge retention dynamics of nanocrystal memory devices is important in optimization of device design. Capacitance spectroscopy on PECVD grown germanium nanocrystals embedded in a silicon oxide matrix was performed. Dynamic measurements of discharge dynamics are carried out. Charge decay is modelled by assuming storage of carriers in the ground states of nanocrystals and that the decay is dominated by direct tunnelling. Discharge rates are calculated using the theoretical model for different nanocrystal sizes and densities and are compared with experimental data. Experimental results agree well with the proposed model and suggest that charge is indeed stored in the quantized energy levels of the nanocrystals.