  The most popular progenitor model for short duration Gamma-Ray bursts (sGRBs)
is the merger of two compact objects. However, the short GRB population exhibit
a certain diversity: some bursts display an extended emission (EE), continuing
in soft $\gamma$-rays for a few hundreds of seconds post the initial short
pulse. It is currently unclear whether the origin of such bursts is linked to
compact object mergers.
  Within the merger hypothesis, the redshift ($z$) distribution of short GRBs
is influenced by the merger delay time, i.e., time elapsed between the merger
and the formation of the binary star system, which is dominated by the
time-scale for gravitational wave losses during the compact binary phase. We
examine redshift distributions of short GRBs with extended emission to see
whether their formation channel requires considerable delay post the star
formation episode. Our results show that the $z$ distribution of EE bursts is
consistent with the merger model. We attempted to compare the delay time
distribution of the EE and the non-EE short bursts. However, no statistically
significant difference could be seen within the limited sample size.
