It was basically invented then, but vacuum tubes were still a better option even when transistors came into use in the 1950s. It took until a lot of extra work was done on semiconductors and other developments before they really became viable in the 1960s. Transistors really were more useful for making computers smaller in the 1950s, hearing aids, and to a degree some radios, but it took until the late 50s-early 60s to really start beating out tubes for radios. Part of that was the development of better production processes for silicon that resulted in greater purity that improved performance, plus improvements in basic design.