Modulation Doping of Silicon using Aluminium-induced Acceptor States in Silicon Dioxide

TL;DR

This paper introduces a novel modulation doping technique for silicon using aluminium-induced acceptor states in silicon dioxide, enabling effective doping at the nanoscale and improving hole conduction for photovoltaic applications.

Contribution

It presents a new heterostructure modulation doping method for silicon that leverages aluminium acceptor states in silicon dioxide, overcoming nanoscale doping challenges.

Findings

Successful creation of heterostructure modulation doping in silicon.

Enhanced hole carrier generation via aluminium-induced acceptor states.

Improved carrier lifetime in silicon heterostructures.

Abstract

All electronic, optoelectronic or photovoltaic applications of silicon depend on controlling majority charge carriers via doping with impurity atoms. Nanoscale silicon is omnipresent in fundamental research (quantum dots, nanowires) but also approached in future technology nodes of the microelectronics industry. In general, silicon nanovolumes, irrespective of their intended purpose, suffer from effects that impede conventional doping due to fundamental physical principles such as out-diffusion, statistics of small numbers, quantum- or dielectric confinement. In analogy to the concept of modulation doping, originally invented for III-V semiconductors, we demonstrate a heterostructure modulation doping method for silicon. Our approach utilizes a specific acceptor state of aluminium atoms in silicon dioxide to generate holes as majority carriers in adjacent silicon. By relocating the dopants from silicon to silicon dioxide, Si nanoscale doping problems are circumvented. In addition, the concept of aluminium-induced acceptor states for passivating hole selective tunnelling contacts as required for high-efficiency photovoltaics is presented and corroborated by first carrier lifetime measurements.