The phase of after depolarization is characterized by:

The slower rate of repolarization toward the later pa has been described as After depolarization. The initial rate of repolarization is rapid. This is due to a greater concentration gradient for K+ to move out. However, as the K+ moves out, two things happen: Concentration gradient for K+ will narrow. Thus, rate of K+ efflux will decrease. The K+ that moved out will cause accumulation of positive charges (carried by K+) just on the outside of the membrane.