Radiation-Induced Defect Reactions in Tin-Doped Ge Crystals

Abstract

We have recently shown that Sn impurity atoms are effective traps for vacancies (V) in Ge:Sn crystals irradiated with MeV electrons at room temperature [V.P. Markevich et al., J. Appl. Phys. 109 (2011) 083705]. A hole trap with 0.19 eV activation energy for hole emission to the valence band (Eh) has been assigned to an acceptor level of the Sn-V complex. In the present work electrically active defects introduced into Ge:Sn+P crystals by irradiation with 6 MeV electrons and subsequent isochronal annealing in the temperature range 50-300 °C have been studied by means of transient capacitance techniques and ab-initio density functional modeling. It is found that the Sn-V complex anneals out upon heat-treatments in the temperature range 50-100 °C. Its disappearance is accompanied by the formation of vacancy-phosphorus (VP) centers. The disappearance of the VP defect upon thermal annealing in irradiated Sn-doped Ge crystals is accompanied by the effective formation of a defect which gives rise to a hole trap with Eh= 0.21 eV and is more thermally stable than other secondary radiation-induced defects in Ge:P samples. This defect is identified as tin-vacancy-phosphorus (SnVP) complex. It is suggested that the effective interaction of the VP centers with tin atoms and high thermal stability of the SnVP complex can result in suppression of transient enhanced diffusion of phosphorus atoms in Ge.

Growth and applications of GeSn-related group-IV semiconductor materials

“…Reference numbers corresponding to index are a [126], b [127], c [128], d [129], e [128], f [130], g [131], h [132], i [133], j [125], k [124], l [134], m [135], and n [136]. …”

“…The Sn and vacancy complex formed not only Sn–V but also Sn n V m clusters. After annealing at temperatures higher than 125 °C, an SnVP complex is formed by the interaction of mobile V–P complexes with Sn [132]. Furthermore, Sn–V-related defects have been observed in an Sn ion-implanted Ge, as shown in figure 15 [142].…”

Growth and applications of GeSn-related group-IV semiconductor materials

“…The origins of these defects may be vacancies, interstitials, impurities, or various vacancy complexes, among others. Table 1 shows a summary of the defects observed using the deep level transient spectroscopy (DLTS) technique [124][125][126][127][128][129][130][131][132][133][134][135][136]. Thus, elaborate control of the defect formation in the Ge LSI process is necessary because Ge-Ge bonds are weaker than those in the conventional Si case.…”