Study of the deep level related to a platinum-dihydrogen complex in Si by capacitance transient spectroscopy under uniaxial stress

We have applied a novel technique to combine isothermal deep-level transient spectroscopy (DLTS) with the application of uniaxial compressive stress to studying the structure of a platinum- and hydrogen-related defect, which has a gap state at 0.14 eV below the conduction band in Si. The application of 〈100〉 and 〈111〉 stresses split the DLTS peak of the defect into two components with intensity ratios of 2.3:1 and 1.1:1, respectively, which were ratios of short- to long-time components. Under 〈110〉 stress, the peak split into three components with an intensity ratio of 0.8:3.7:1. Comparing this splitting pattern to the piezospectroscopic theory of Kaplyanskii, we have uniquely determined that the defect has the orthorhombic symmetry with the C_2v point group, and have identified the defect as the Pt-H₂ complex previously identified by Uftring et al. [Phys. Rev. B 51 (1995) 9612]. We also observed that the defect was reoriented above 80 K along the applied uniaxial stress. Such reorientation occurred only when the defect level was not occupied by an electron. Our observation strongly suggests that the local motion of hydrogen around the Pt atom is remarkably affected by the charge state of the defect.