Grading effects in semiconductor nanowires with longitudinal heterostructures

TL;DR

This paper theoretically examines how graded interfaces in semiconductor nanowires influence electron confinement, revealing unique potential profiles and the possibility of magnetic-field-induced confinement and phase transitions.

Contribution

It introduces a detailed theoretical model for graded interfaces in nanowires, showing their impact on electron confinement and phase transitions, extending previous abrupt interface models.

Findings

Graded interfaces create cusped potential profiles leading to interfacial electron confinement.

Magnetic fields can induce type-I to type-II transitions in electron confinement.

Interfacial effects significantly alter carrier localization compared to abrupt interface models.

Abstract

The role of graded interfaces between materials in a cylindrical free-standing quantum wire with longitudinal heterostructures is theoretically investigated, by solving the Schr\"odinger equation within the effective mass approximation. Previous work on such wires with abrupt interfaces have predicted that, as the wire radius is reduced, the effective potential along the growth direction is altered and might lead to a carrier confinement at the barriers, as in a type-II system. Our results show that when graded interfaces are considered, such potential acquires a peculiar form, which presents cusps at the interfacial regions, yielding to electron confinement at interfaces. Numerical results also show that, in some special cases, interfacial confinement and type-I to type-II transitions can also be induced by applying a magnetic field parallel to the wire axis.