SILICON IMPLANTED WITH MEV(12)C IONS - TEMPERATURE-DEPENDENCE OF DEFECT FORMATION AT LOW-DOSES

Si(100) samples of n-type have been implanted with 3.6 MeV C-12 ions u sing doses < 10(7)-2 x 10(9) cm(-2). During implantation, the samples were kept at temperatures ranging from -110 to 400 degrees C, and subs equently, deep level transient spectroscopy (DLTS) was used for charac terization of the samples. The DLTS spectra are dominated by the peaks normally associated with the vacancy-oxygen and divacancy (V-2) cente rs. The strength of the peaks changes with temperature and in particul ar, the level originating from the doubly negative charge state of V-2 increases by similar to 50% between -110 and 300 degrees C. This is n ot attributed to an increase in the V-2 concentration, but, merely ref lects a relaxation of the strain in the lattice surrounding the V-2 ce nters. Above similar to 300 degrees C V-2 ceases to be stable and new energy levels appear. In particular, for doses below 10(7) cm(-2) at 4 00 degrees C a new major peak emerges close to the middle of the bandg ap (similar to 0.57 eV below the conduction band edge, E(c)). The iden tity of E(c) -0.57 eV level is not known but it involves most likely i mpurities present in the as-grown material.