The characteristics of InGaAs quantum dot laser diodes have been investigated by inserting InGaAs wells of different thicknesses in the active zone. The simulation results indicated that the maximum output power of the InGaAs quantum dot laser diode with a 0 nm-thick InGaAs well is 0.72 W at an injection current of 1.1 A. However, the quantum dot laser diode with a 12 nm-thick InGaAs well has a maximum electro-optical conversion efficiency of 40.6%. The properties of carrier transport in the active zone were analyzed via the potential difference of the band offset among potential barrier, potential well, and waveguide layer. It is observed that electron leakage increases owing to the inserted InGaAs well. Auger recombination not only increases the carrier injection efficiency but also is acts as the key factor of carrier loss in the active zone. Moreover, the inserted InGaAs well can improve carrier transport in the active zone and increase the carrier utilization efficiency. The power-loss mechanism of the quantum dot laser diode was elucidated from the optical and carrier losses. It is found that optical loss is the key factor that affects the output power.