Precipitation‐Induced Currents and Generation‐Recombination Currents in Intentionally Contaminated Silicon P+N Junctions

The effects of impurities such as gold, iron, copper, nickel, tantalum, and tungsten on junction reverse I ‐ V characteristics were investigated using DLTS (deep level transient spectroscopy), TSCAP (thermally stimulated capacitance), I ‐ V , C ‐ V , and I ‐ T measurements. In almost all cases, the reverse I ‐ V characteristics consisted of two components; a normal Shockley‐Read‐Hall (SRH) generation component and a soft leakage component which dominates the SRH component above a given onset voltage. Only the SRH component can be detected with the DLTS and TSCAP methods. The soft leakage currents were ascribed to the presence of impurity precipitates lying near the metallurgical junction of the devices. Soft leakage currents measured at 80°K were fitted to a Fowler‐Nordheim field‐emission model. Localized electric field values near the precipitates of the order of 10 6 –10 7 V/cm were obtained by this analysis. These values could be correlated with the possible shape of the precipitates. The distribution of the SRH generation centers within the active regions of the devices and the activation energies of the emission rates of above‐mentioned impurities were measured using the DLTS technique. The following results were obtained: Au 0.55 eV ( c ), Fe 0.57 eV ( c ); Cu 0.2 eV ( c ), 0.49 eV ( v ), 0.41 eV ( v ); Ni 0.19 eV ( c ), 0.36 eV ( c ); Ta 0.21 eV ( c ); and W 0.25 eV ( c ), 0.28 eV ( c ), respectively. Here c and v represent measurements from the conduction band and valence band, respectively.