Scientific manuscripts; research progress reports; notes and data sheets; thesis. Materials relate to semiconductor research and document research on germanium and silicon at Purdue University under the direction of Lark-Horovitz, primarily the World War II project on the development of germanium rectifiers. Topics in the field of semiconductors include acceptors and donors, heat conductivity, pressure effects, resistivity, electron scattering, irradiation, electrical properties, and thermoelectric power measurements. The collection includes typescripts on the history of germanium research at Purdue University by Lark-Horovitz, and a manuscript biography of Lark-Horovitz by an associate, Vivian A. Johnson. Also included is a report on semiconductor research in Europe written after a trip in 1950.