"expanded the breadth of" is correct and can be used in written English.
It is usually used to describe an increase in the scope of something. For example, "The company expanded the breadth of its product offerings to meet changing customer needs".
During his years as Editor, he expanded the breadth of the Journal to include many articles on international issues.
In particular, the surge of interest in nanomaterials has significantly expanded the breadth of research on magnetic nanoparticles (MNPs) during the recent decade.
John Crane has expanded the breadth of its technology base by integrating Specac, a company that designs and manufactures specialist measuring and analysis equipment.
In this paper we present eight features of our co-operation with industry that have significantly expanded the breadth of the UO laboratory experiences for the Chemical Engineering students and faculty.
This line with many non-hamburger sandwiches, including chicken and fish significantly expanded the breadth of the BK menu.
The new product line significantly expanded the breadth of the BK menu with many non-hamburger sandwiches, including new chicken and fish offerings.
Not in the first two episodes, which expand the breadth of the books without sacrificing their buoyancy or innocence.
"We're expanding the breadth of the program to include other areas," said Jeremy Soffin, a spokesman for the Metropolitan Transportation Authority.
He was a man of diverse interests, with a keen curiosity and a continual desire to expand the breadth of his knowledge and experience.
"Vubiquity remains focused on expanding the breadth of our managed services and technical solutions that today support content and service providers worldwide," said Antonellis.
