Defect study of Zn-doped p-type gallium antimonide using positron lifetime spectroscopy

TLDR: In this paper, the positron lifetime measurements were performed on the as-grown sample at temperature varying from 15 K to 297 K, and a positron trapping center having a characteristic lifetime of 317 ps was identified as the neutral positron-related defect.

Abstract: Defects in p-type Zn-doped liquid-encapsulated Czochralski\char21{}grown GaSb were studied by the positron lifetime technique. The lifetime measurements were performed on the as-grown sample at temperature varying from 15 K to 297 K. A positron trapping center having a characteristic lifetime of 317 ps was identified as the neutral ${V}_{\mathrm{Ga}}$-related defect. Its concentration in the as-grown sample was found to be in the range of ${10}^{17}\char21{}{10}^{18} {\mathrm{cm}}^{\ensuremath{-}3}.$ At an annealing temperature of $300\ifmmode^\circ\else\textdegree\fi{}\mathrm{C},$ the ${V}_{\mathrm{Ga}}$-related defect began annealing out and a new defect capable of trapping positrons was formed. This newly formed defect, having a lifetime value of 379 ps, is attributed to a vacancy\char21{}Zn-defect complex. This defect started annealing out at a temperature of $580\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}.$ A positron shallow trap having binding energy and concentration of 75 meV and ${10}^{18} {\mathrm{cm}}^{\ensuremath{-}3},$ respectively, was also observed in the as-grown sample. This shallow trap is attributed to positrons forming hydrogenlike Rydberg states with the ionized dopant acceptor Zn.

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FIG. 3. ~a! and ~b! show the positron trapping rates of th VGa-related defect and the vacancy-Zn complex having charact tic lifetime value of 379 ps as a function of the annealing tempe ture, respectively. The defect concentrations were also calcul and are plotted at the righty axis.

FIG. 1. Fitted positron lifetime parameters of the as-grown Z doped GaSb sample as a function of the measuring tempera The long lifetime componentt2 has constant value of 31867 ps. The solid curve was calculated from the model involving a vaca trap and a shallow trap.

FIG. 2. Fitted lifetime parameters of the Zn-doped GaSb sam as a function of the annealing temperature are shown in circle solid line. The two annealing stages are clearly seen at tempera of 300 °C and 580 °C. The 300 °C annealing is related to the an out of theVGa-related defect and the formation of a vacancy-ty defect complex comprising the Zn dopant. The 580 °C annea corresponds to the anneal out of this new defect. The average time as a function of the annealing temperature for the undo GaSb sample is shown as triangle and dotted line in~d!.