Dr. Robert N. Hall


Oral History – Robert Hall



A chance observation while measuring one of the aforementioned ingots led me to the concept of a PIN rectifier and to the alloying method of producing PIN power devices.  I proved these ideas out of converting tens of KW of AC into DC in my lab, using water-cooled Ge diodes.  The same principal was applied by others using Si instead of Ge, and these are used today to power locomotives and in HVDC power transmission terminals.  I made measurements of these PIN rectifiers over a wide range of temperature and current to figure out how they worked. However, I was unable to account for their characteristics using the accepted model for electron-hole recombination as described by Shockley; there was a factor of 2 missing in the exponential.  Finally, I figured out that a two-step transition through a deep level recombination center near the middle of the forbidden gap would explain everything, including observations on minority carrier lifetimes that I and others were measuring at the time.  I reported this and the idea was picked up by Shockley and Read at BTL who produced a much more extensive analysis of recombination.  This mechanism is now known as “Shockley-Read-Hall” (SRH) recombination (or sometimes HSR recombination, depending on who you are talking with). Anyhow, it is fashionable to cite this reference when reporting anything dealing with recombination, so it has had a lot of mileage.








Oral History – Robert Hall (Continued)


In 1962 I heard a report of intense and highly efficient infrared emission from GaAs junctions and realized that these results suggested that a semiconductor laser might be possible.  I came up with a structure that we could build and I thought might work and rounded up a group with the necessary talents to tackle the job.  We succeeded in demonstrating the first semiconductor laser, which included Fabry-Perot mirrors.  Simultaneously, IBM reported stimulated emission with pronounced spectral narrowing, which was very close, and resulted in laser patents for both organizations.  The German courts only allow one inventor.  I was invited to testify there, with the result that we (GE) were awarded the invention.  That was all very excited, with the results documented elsewhere.


IN 1977, I began an investigation of silicon photovoltaic technology.  I was the principal Investigator in a JPL (DOE) sponsored development program in Sheet Silicon Growth in 1976-1977 and was the inventor of the “Polka-Dot Solar Cell”.  Following this, I resumed studies of hydrogen-related defect complexes in germanium, working out the kinetics of hydrogen pairing with silicon and oxygen, and of hydrogen molecule formation following a quench from an elevated temperature.    More recently, I undertook a study of precipitate defects which form during processing of silicon integrated circuits.  Since retiring from GE in 1987, I have been engaged as a consultant in several areas of semiconductor technology.


Go To Hall Oral History, Page 3


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