emories of early days in solid state physics reads as a treatise on what we should now call'deep levels, a subject only now coming into prominence among semiconductor physicists. Copper oxide was our typical'semiconductor. I believe it was only during the war, as a result of wartime work in the United States that it was first realized that silicon and germanium were emiconductors and notpoor'metals F Seitz comments as follows i guess i deserve as much credit as anyone for getting the physics of silicon and germanium, including the determination of basic parameters, on the right track. This was done early in the war, as is indicated in the last paragraph starting on page 8 of Volume 15 of the Radiation Laboratory series The background history of the situation seems to be the following. It was well known from early radio days that raw commercial(metallurgical) silicon had active spots that could provide excellent rectification in the usual cat-whiske arrangement. In fact, such rectifiers were used for experimental work as research progressed into the multi-megacyele range Silicon rectifiers were adapted for radar work by British Thompson-Houston on a classified basis in the late 1930 and by the Germans, presumably at about the same time. In fact, there is an article in the Zeitschrift fair Physik describing the observational characteristics of such rectifiers in 1939 or 1940. The British material was relatively crude and was very heavily doped with aluminium to give it some degree of uniformity and to make it p type The British technology was taken over in the United States as a result of the generation of cooperative programs early in the war, and I was asked, probably in the middle of 1941, if I would establish a research group at the University of Pennsylvania which would attempt to find out more about the workings of the material. Perhaps I should add that the Bell Laboratories was also deeply in volved and had a group of metallurgists under J. H. Scaff which was trying to refine metallurgical grade silicon by selective crystallization-a fairly hopeless task at that time. This was long before the days of zone refining. I decided that we ought to start completely anew and persuaded the Dupont company to initiate a program to produce a relatively pure grade of silicon from purified silicon tetrachloride We began experiments in Philadelphia on the effect of various additions to this material, using whatever elements we could lay our hands on and carrying through a combination of conductivity(four-electrode)and Hall affect measure ments at various temperatures. This gave us a chance to map out the general characteristics of the material containing various additions. Needless to say, our initial interest was to cover as much ground as possible rather than to achieve orecision to many decimal point I should add that in the course of this work we did some rudimentary research with fairly pure germanium obtained from the University of Chicago. We also discovered some papers in the literature describing research carried out by physical chemists at Cornell University in the 1920s on the physical properties of relatively pure germanium prepared there. An analysis of their relatively