  We report the carrier dynamics and recombination coefficients in
single-quantum-well semipolar $(20\bar 2\bar 1)$ InGaN/GaN light-emitting
diodes emitting at 440 nm with 93% peak internal quantum efficiency. The
differential carrier lifetime is analyzed for various injection current
densities from 5 $A/cm^2$ to 10 $kA/cm^2$, and the corresponding carrier
densities are obtained. The coupling of internal quantum efficiency and
differential carrier lifetime vs injected carrier density ($n$) enables the
separation of the radiative and nonradiative recombination lifetimes and the
extraction of the Shockley-Read-Hall (SRH) nonradiative ($A$), radiative ($B$),
and Auger ($C$) recombination coefficients and their $n$-dependency considering
the saturation of the SRH recombination rate and phase-space filling. The
results indicate a three to four-fold higher $A$ and a nearly two-fold higher
$B_0$ for this semipolar orientation compared to that of $c$-plane reported
using a similar approach [A. David and M. J. Grundmann, Appl. Phys. Lett. 96,
103504 (2010)]. In addition, the carrier density in semipolar $(20\bar 2\bar
1)$ is found to be lower than the carrier density in $c$-plane for a given
current density, which is important for suppressing efficiency droop. The
semipolar LED also shows a two-fold lower $C_0$ compared to $c$-plane, which is
consistent with the lower relative efficiency droop for the semipolar LED (57%
vs. 69%). The lower carrier density, higher $B_0$ coefficient, and lower $C_0$
(Auger) coefficient are directly responsible for the high efficiency and low
efficiency droop reported in semipolar $(20\bar 2\bar 1)$ LEDs.
