 Rational map with Julia set equal to the Riemann sphere

For every $d\ge 2$, choose a $d$th root of unity $r\ne 1$ with $d|1-r|>1$, put $a=1-r$, and setIts only critical points are $0$ and infinity, and both land on the repelling fixed point $r$. The postcritically finite map has no possible Fatou component, so its Julia set is the whole sphere.