Influence of imperfections on tunneling rate in $\delta$-layer junctions

TL;DR

This paper investigates how various imperfections, especially charged impurities, affect tunneling rates in doped silicon devices, revealing that impurities can significantly alter tunneling behavior even at large gaps.

Contribution

It provides a detailed analysis of how different imperfections influence tunneling rates in $ ext{δ}$-layer junctions, highlighting the critical impact of charged impurities.

Findings

Charged impurities can change tunneling rates by over an order of magnitude.

Most imperfections have moderate effects on tunneling rates.

Tunneling rate depends strongly on the impurity's charge sign.

Abstract

The atomically precise placement of dopants in semiconductors using scanning tunneling microscopes has been used to create planar dopant-based devices, enabling the exploration of novel classical or quantum computing concepts, which often require precise control over tunneling rates in their operation. While the geometry of the dopants can be defined to sub-nanometer precision, imperfections can still play a significant role in determining the tunneling rates. Here, we investigate the influence of different imperfections in phosphorous $\delta$-layer tunnel junctions in silicon: variations of $\delta$-layer thickness and tunnel gap width, interface roughness, and charged impurities. It is found that while most of the imperfections moderately affect the tunneling rate, a single charged impurity in the tunnel gap can alter the tunneling rate by more than an order of magnitude, even for relatively large tunnel gaps. Moreover, it is also revealed that the tunneling rate strongly depends on the electrical charge sign of the impurity.