The Effect of Applied Electric Field on Diffusion of Impurities in Gallium Arsenide

Abstract

AbstractElectrical migration of lithium and copper in gallium arsenide is studied. It is shown that lithium (between 740 and 980°C) and copper (between 820 and 1000°C) migrate in n‐type gallium arsenide as positive ions with a charge of less than +1. The decrease of the ionic charge is due to ion drag by the electrons. In heavily doped p‐type gallium arsenide, copper again migrates in the form of positive ions but in this case with a charge close to +1. This is due to the ion drag by the electrons being almost balanced by the drag from the holes which acts in the opposite direction. Experimental evidence suggests that thermal conversion in gallium arsenide is caused by copper diffusing from outside. Copper can be successfully removed from specimens by heating them in an applied dc electric field. Electrical migration of zinc and cadmium is also studied. Cadmium is shown to migrate in the form of positive ions. In the temperature range 830 to 1130°C, zinc also migrates as positive ions, the effective mobility decreasing with temperature. This temperature dependence of the mobility is in agreement with a theory of the ion drag effect.