 He continued his work on magnetrons and said he came close to co-inventing the transistor.If he and his co-workers had placed their contacts on a single crystal of zircon rather than working with multiple crystals, they would have beaten Shockley's team, also at Bell Labs.Mueller increasingly believed that to move up in the hierarchy of the Labs he would need a PhD, and he began working towards this goal on a part-time basis at Princeton University, getting up every morning at around 5 o'clock and driving to Princeton to take a couple of courses before driving back down to Holmdel to work all day at Bell Labs.