What are the substrate requirements for heteroepitaxial growth?
Heteroepitaxy is an advanced crystal growth technology. It refers to the process of growing a thin film or epitaxial layer with a different crystal structure or chemical composition from the substrate material on a specific substrate material, that is: on a specific substrate material. A substrate of material grows on another material.
Heteroepitaxy has the following requirements for the substrate
Lattice matching: To achieve high-quality heteroepitaxy, the lattice constant of the epitaxial layer should be as close as possible to that of the substrate material. Lattice mismatch can cause stress and defects, affecting device performance. If the mismatch is large, a buffer or graded layer may be needed to alleviate the problem caused by the lattice mismatch.
Thermal expansion coefficient matching: The thermal expansion coefficients of the epitaxial layer and the substrate material should match each other to avoid residual thermal stress, interface dislocation, and even rupture of the epitaxial layer when the epitaxial layer is cooled from the growth temperature to room temperature.
Chemical compatibility: There should be good chemical compatibility between the epitaxial layer and the substrate material. There should be no chemical reaction between the substrate and the epitaxial layer, and no large amount of dissolution. In order to avoid changes in the chemical composition and structure of the epitaxial layer during the growth process.
Electronic properties: The material of the epitaxial layer should have the required electronic properties, such as energy band structure, carrier mobility and doping efficiency, to meet the performance requirements of the specific device.
Mechanical strength: The substrate should have sufficient mechanical strength to support the growth of the epitaxial layer and remain stable during subsequent device processing.
Thermal conductivity: The thermal conductivity of the substrate material is also an important factor, especially in applications that require efficient heat dissipation. Good thermal conductivity contributes to device stability and longevity under high-power operation.
Heteroepitaxial technology has great potential in improving device performance, reducing costs and realizing new devices. Therefore, when selecting epitaxial layers and substrate materials, the above requirements need to be comprehensively considered to achieve optimal device performance and manufacturing efficiency.
