At that time they were experimenting with different kinds of transistors -- pnp, npn, the semi-conductor material, etc. The IBM history "IBM's Early Computers" by Bashe et al goes into some detail on this.
BTW, in the late 1940s they had trouble with vacuum tubes for digital applications. What would work fine in audio was not good enough for digital. IBM spent a lot of time developing specs and considered making its own tubes, but the tube makers were able to meet the needs.
IBM spent considerable efforts on this, the above book describes it. I do believe, however, it was more on the packaging of the transistors on cards than making the transistors themselves; IBM bought transistors from others at that time. But IBM did research the manufacturing process too.
Well, the IBM history (and also "IBM's System 360" book) might have a bit of bias since they were written by the research people. However, it does seem that Tom Watson Jr drastically improved the research environment and many useful products came out of it. They invented the disk drive, and developed cost-effective packaging for semi-conductors (SMS cards and later SLT chips) that allowed IBM to take the lead of the industry from a losing position.
I do recommend the two above books on IBM (published by MIT Press). Much interesting technical information. There's a third, "Building IBM" by Emerson Pugh which is a good summary history of the company.
When did the "Solid State" computer come out? Was that the "Univac III"?
Philco made its own computers, too. At some point Ford Motor Co took them over and the name Philco has faded from the scene. They made consumer electronics but I didn't think their quality was as good as other brands.