Radiation Induced Defect Levels in Highly Doped n-Type Si_(1-x)Ge_x Strained Layers

摘要

Deep Level Transient Spectroscopy (DLTS) studies of 2-MeV proton induced deep level defects have been performed in highly phosphorous-doped strained Si_(1-x)Ge_x layers with x = 0.13 grown by Chemical Vapor Deposition (CVD). Due to the high doping concentration, 1 ÷ 3 * 10~(17) cm~(-3), the layers have been irradiated with high doses from 10~(14) cm~(-2) to 7 * 10~(15) cm~(-2) in order to produce a measurable concentration of electrically active centers. It has been found that the irradiation results in formation of a dominant peak in the DLTS spectra that corresponds to a deep level located at 0.47 eV below the conduction band edge. Isochronal 20-min annealing studies of the observed deep level have revealed that at 100 °C ÷ 200 °C the peak maximum shifts to lower temperature that corresponds to another level at 0.42 eV below the conduction band edge which remains stable up to 250 °C ÷ 300 °C. These two levels have been identified as associated with VP and V_2. The effect of stress and layer composition on their properties is discussed.