Norman H. Ditrick


Oral History – Norm Ditrick (Continued)


In 1956 or 1957, the drift transistors were marketed by RCA – we were in the lead in terms of frequency performance for quite a while.  These transistors were made using a special process to prepare the substrate, which was intrinsic germanium that was doped by diffusion with arsenic.  It was difficult controlling the thickness of the substrate, since we had to etch off one side of the diffused arsenic.  I built almost every one of these devices in the development stage.  After we were satisfied with the design, more units were made in the model shop and then finally in production.  This work probably started in Harrison, and then was finalized after we had moved to Somerville (the Semiconductor Group moved to Somerville NJ in 1956, I think).       


So my main assignments had been in early transistor device design and assembly, starting with point contact transistors in 1952, and then with junction and drift transistors up through 1957.  Now these early transistors started out with something called a solder-seal, which was really a compression seal using a solder ring around the metal can.  This worked pretty good as encapsulation.  The earlier Araldite epoxy was not very good at all for hermetic sealing. We even tried putting some kind of “glop” on the junctions before coating with epoxy – this didn’t work either.  The solder-seal was the best solution. 


The next major program I worked on was gallium arsenide junction transistors.  Unfortunately, this program was not successful.  RCA had received a contract       




Oral History – Norm Ditrick (Continued)


from the government to go directly from germanium to gallium arsenide.  I think this was a mistake because many other companies were working with silicon and they were off to a big head start on RCA.        We had been able to sell the government on the idea of gallium arsenide because this material is basically insensitive to temperature, even more than silicon. Our management was able to convince the government that this material was very well suited for military applications because it could be used in any environment.  Unfortunately, we discovered that you really can’t make junction transistors using this material; what you end up with are light emitting junctions, and this light takes power away from the transistor junctions and yields transistors with no gain.  So, we were making gallium arsenide light emitting devices, and what we wanted were transistors.  The gains for these devices, if they worked at all, was 3 or 4, while beta from comparable germanium devices was as high as 100.   This program was not successful and I don’t believe we even got as far as building any developmental units. RCA had a system of using a “TA” number on developmental devices, and then successful devices would go into production and be assigned a “2N” number.  The gallium arsenide transistors were never assigned “TA” numbers as far as I know.   All this work on gallium arsenide transistors was done at Somerville.  




Go To Ditrick Oral History, Page 4


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