Direct Observation of Electron Capture and Reemission by the Divacancy via Charge Transient Positron Spectroscopy

Abstract

Electron capture during forward bias and reemission at zero bias by divacancies in the depletion region of a silicon diode structure at room temperature have been studied for the first time using monoenergetic positrons. The positron response increases essentially linearly with electron current, as a result of increased positron trapping by negatively charged divacancies. The measurements indicate that ≤1% of the divacancies become negatively charged in the steady state at a forward bias of 1 V. Changes in the mean positron response when applying a square wave bias to the sample (1 V forward bias and 0 V, duty cycle 1:4, times at 0 V in the range 0.1-100 μs), were consistent with a rapid conversion of doubly to singly charged divacancies (in ∼10(1) ns), followed by slower defilling of the singly charged divacancies with a time constant of ∼10(1) μs. These ac measurements allow determination of the relative populations of singly and doubly charged divacancies. The results provide confirmation of consistency between the positron's response to the silicon divacancy and previously extracted capture and emission kinetics determined through charge transient measurements and assigned to the same defect. The possibility of combining these two, orthogonal techniques suggest a promising new and powerful approach to defect spectroscopy in which the structure and electrical properties of a defect may be determined in a single measurement.

Identification of Point Defects in Multielement Compounds and Alloys with Positron Annihilation Spectroscopy: Challenges and Opportunities

“…[34][35][36][37][38][39][40][41][42] More recent advances include the studies on the asymmetric stability of vacancy defects in GaSb, [43,44] the possibility of detecting and identifying small substitutional impurities such as Li Zn in ZnO and Be Ga in GaN, [45][46][47] and studying transient charge transfer phenomena induced by electrical or optical excitation of defects. [48,49] For more comprehensive reviews on studying point defect in metals and semiconductors with positron annihilation techniques, it is advisable to browse through recent reviews. [7,[50][51][52][53] Challenges in defect identification arise in multielement nondilute alloys and compounds for four main reasons.…”

Cascade phonon-assisted trapping of positrons by divacancies in n-FZ-Si(P) single crystals irradiated with 15 MeV protons

“…The study of divacancies in silicon using the methods of the positron annihilation spectroscopy is an area of rather intensive activity (see, e.g., [5] and references therein). Having combined the data obtained by both the positron annihilation lifetime and Hall's effect measurements, we have estimated the positron trapping cross-section by divacancies and showed that the cascade phonon-assisted mechanism underlies its thermal dependency.…”