Defect-dopant interaction in n- and p-type diamond and its influence on electrical properties

The electrical properties of semiconducting diamond are governed by the material quality, i.e. by the presence of defects. Here we report on the results of a comparative study on the dependence of the electrical properties of n- and p-type doped diamond layers on the density of defects present in the layer. Three main points are addressed: (1) the nature and conductivity-type of the defects, (2) the influence of the defects on the electrical characteristics of the layer (compensation, passivation of the dopants) and (3) the comparison between the defect/dopant interaction in the p- vs. n-type samples. For that end, defects are introduced by implanting ever-increasing doses of hydrogen through homoepitaxially B- and P doped diamond layers, leaving in the layer well-known amounts of point defects. Following each implantation dose, the electrical characteristics of the sample are evaluated by using resistivity and Hall effect measurements over a wide temperature range. For the first time, we demonstrate by means of electrical measurements the amphoteric nature of the defects introduced in the B- and P-doped diamond films, i.e. the fact that defects may exist in different charge states, depending on the conductivity type of the doped layers; the defects being in a positive charge state in B-doped layers and in a negative state in P-doped diamond; hence both impurities are compensated by the irradiation induced defects.