请问这句话怎么翻译好?尤其是“we have witnessed.”该怎么翻译?In the past few years we have witnessed intensive research activity in the development of a variety of electronic devices based on the wide band gap refractory semiconductor GaN, and its related alloys and heterostructures.

请问这句话怎么翻译好?尤其是“we have witnessed.”该怎么翻译?
In the past few years we have witnessed intensive research activity in the development of a variety of electronic devices based on the wide band gap refractory semiconductor GaN, and its related alloys and heterostructures.