  The quantum-confined Stark effect in InAs/In(Ga)As quantum dots (QDs) using
non-intentionally doped and p-doped QD barriers was investigated to compare
their performance for use in optical modulators. The measurements indicate that
the doped QD barriers lead to a better figure of merit $(FoM)$, defined as the
ratio of the change in absorption $\Delta\alpha$ for a reverse bias voltage
swing to the loss at $1 V$ $\alpha(1 V)$, $FoM=\Delta\alpha/\alpha (1 V)$. The
improved performance is due to the absence of the ground-state absorption peak
and an additional component to the Stark shift. Measurements indicate that
p-doping the QD barriers can lead to more than a 3$\times$ increase in FoM
modulator performance between temperatures of -73 $\deg$C to 100 $\deg$C when
compared with the stack with NID QD barriers.
