heterostructures

A heterostructure is a material system formed by combining layers or regions of materials with differing properties, such as band gaps, lattice constants, or refractive indices. Interfaces between these materials can give rise to electronic, optical, and mechanical phenomena that differ from those of the bulk constituents. Heterostructures are fundamental in semiconductor physics and optoelectronics, enabling device functionalities not possible in a single material.

Common forms include heterojunctions, quantum wells, and superlattices, as well as more complex low-dimensional structures like quantum wires and quantum dots. The electronic and optical behavior at an interface is governed by band alignment, typically categorized as type I, type II, or type III, which determines carrier confinement and recombination. Lattice mismatch between adjacent layers can induce strain, which can be engineered to tailor electronic properties.

Fabrication relies on epitaxial growth methods that produce abrupt, high-quality interfaces. Techniques such as molecular beam epitaxy and metal-organic chemical vapor deposition allow precise control of layer thickness at the atomic scale.

Applications span high-performance transistors, laser diodes, light-emitting devices, infrared and visible photodetectors, and solar cells, as well as emerging quantum information platforms. Challenges include managing lattice mismatch, defects at interfaces, interdiffusion between layers, and thermal and mechanical stresses.