Metal-Semiconductor (M/S) heterojunctions, better known as Schottky junctions play a crucial role in modern electronics. At present, the mechanisms behind the M/S junctions are still a subject of discussion. In this work, we investigate the interfaces between semiconducting crystalline Si and amorphous metallic indium, Si{0 0 1}/a-In and Si{1 1 1}/a-In using both ab initio molecular dynamics simulations and a Schottky-Mott approach. The simulations reveal the formation of a distinct border between the Si substrates and amorphous In at the interfaces. The In atoms adjacent to the interfaces exhibit atomic ordering. Charge transfer occurs from In to Si, forming c-Si^−q/a-In^+q charge barriers at the interfaces. This indicates that a crystalline p-Si/a-In heterojunction will have rectifying properties, which agrees with an analysis using the Schottky-Mott model which predicts a Schottky barrier height of 1.3 eV for crystalline p-Si/a-In using the calculated work function for a-In (3.82 eV). We further discuss the interfacial charge transfer, related hole-depletion regions in Si adjacent to the interfaces and the Schottky-Mott approximations.

The recently found crystalline silicon-amorphous boron (c-Si/a-B) heterojunction has been successfully applied in the detection of short-wave UV photons. These detectors play a decisive role in the progress of nanoelectronics fabrication. The c-Si/a-B heterojunction could not be explained using the existing 'instrumentarium' in semiconductor physics. We investigated the c-Si/a-B interfaces using ab initio molecular dynamics simulations. The simulations reveal atomic ordering of the a-B atoms adjacent to both the Si{0 0 1} and Si{1 1 1} substrates. Charge transfer occurs from the interfacial Si to B, thereby forming Si+/B- charge barriers, which induce an electric field in the nearby regions. The obtained information here is helpful in furthering our understanding of the physics behind the c-Si/a-B junctions, as well as driving the development of a new 'instrumentatrium' in solid state physics.

The interest in nanostructures of silicon and its dopants has significantly increased. We report the creation of an ultimately-shallow junction at the surface of n-type silicon with excellent electrical and optical characteristics made by depositing an atomically thin boron layer at a relatively low temperature where no doping of silicon is expected. The presented experimental results and simulations of the ab initio quantum mechanics molecular dynamics prove that the structure of this new type of junction differs from all other known rectifying junctions at this time. An analysis of the junction formation has led to the conclusion that the chemical interaction between the surface atoms of crystalline silicon and the first atomic layer of the as-deposited amorphous boron is the dominant factor leading to the formation of a depletion zone in the crystalline silicon which originates from the surface. The simulation results show a very strong electric field across the c-Si/a-B interface systems where the charge transfer occurs mainly from the interface Si atoms to the neighboring B atoms. This electric field appears to be responsible for the creation of a depletion zone in the n-silicon resulting in a rectifying junction-formation between the n-silicon and the atomically thin boron layer.