Properties of Thermally Treated Germanium

Upon heating a piece of germanium in a vacuum of 10^-6 mm Hg, the following results have been obtained. (1) Below 350^∘{}C, the rectification characteristic is improved. Heating the specimen at a temperature between 400^∘{}C and 600^∘{}C destroys the rectification, which is not recovered completely when it is heated in vacuum. However, heating in an oxygen atmosphere leads to a slight recovery of the rectification.(2) Treatment above 550^∘{}C makes the formation of acceptor levels detectable. With continued heating at 500^∘{}C for about 48 hours, the specimen returns again to n type similar to the original state. The formation and disappearance of acceptor levels were followed when the specimen was quenched from a fixed temperature to room temperature. The equilibrium concentration at the heating temperature was determined to be A=2.5×10²¹exp(-27000/RT) cm^-3.(3) On the assumption that the acceptor levels produced on the surface diffuse into the interior, the data could be fairly well represented with an estimated diffusion coefficient: D=300exp(-37000/RT) cm² sec^-1.(4) The resistivity and Hall coefficient from room temperature to about 200^∘{}C have been measured for several specimens.