  A detailed experimental analysis of the impact of active region design on the
performance of 1300 nm lasers based on InGaAs/InAlGaAs superlattices is
presented. Three different types of superlattice active regions and waveguide
layer compositions were grown. Using a superlattice allows to downshift the
energy position of the miniband, as compared to thin InGaAs quantum wells,
having the same composition, being beneficial for high-temperature operation.
Very low internal loss (~6$cm^{-1}$), low transparency current density of ~500$
A/cm^2$, together with 46$ cm^{-1}$ modal gain and 53 % internal efficiency
were observed for broad-area lasers with an active region based on a highly
strained $In_{0.74}Ga_{0.26}As/In_{0.53}Al_{0.25}Ga_{0.22}As$ superlattice.
Characteristic temperatures $T_0$ and $T_1$ were improved up to 76 K and 100 K,
respectively. These data suggest that such superlattices have also the
potential to much improve VCSEL properties at this wavelength.
