Energetics and carrier transport in doped Si/SiO2 quantum dots

TL;DR

This theoretical study investigates how boron and phosphorus impurities affect the energetics and carrier transport in silicon quantum dots embedded in SiO2, revealing doping site preferences and transport enhancements relevant for optoelectronic applications.

Contribution

It provides new insights into impurity site preferences and their impact on transport properties in doped silicon quantum dots within a SiO2 matrix.

Findings

Doping sites are energetically favored inside the QD for P and at the interface for B.

Doped Si-QDs show reduced voltage threshold and increased current at low voltages.

P-doped Si-QDs exhibit significant transport increase at high voltages.

Abstract

In the present theoretical work we have considered impurities, either boron or phosphorous, located at different substitutional sites in silicon quantum dots (Si-QDs) with diameters around 1.5\,nm, embedded in a SiO2 matrix. Formation energy calculations reveal that the most energetically-favored doping sites are inside the QD and at the Si/SiO2 interface for P and B impurities, respectively. Furthermore, electron and hole transport calculations show in all the cases a strong reduction of the minimum voltage threshold, and a corresponding increase of the total current in the low-voltage regime. At higher voltage, our findings indicate a significant increase of transport only for P-doped Si-QDs, while the electrical response of B-doped ones does not stray from the undoped case. These findings are of support for the employment of doped Si-QDs in a wide range of applications, such as Si-based photonics or photovoltaic solar cells.