  A key component for the realization of silicon-photonics are integrated
lasers operating in the important communications band near 1.55 ${\mu}$m. One
approach is through the use of GaSb-based alloys which may be grown directly on
silicon. In this study, silicon-compatible strained
Ga$_{0.8}$In$_{0.2}$Sb/Al$_{0.35}$Ga$_{0.65}$As$_{0.03}$Sb$_{0.97}$ composite
quantum well (CQW) lasers grown on GaSb substrates emitting at 1.55 ${\mu}$m
have been developed and investigated in terms of their thermal performance.
Variable temperature and high-pressure techniques were used to investigate the
influence of device design on performance. These measurements show that the
temperature dependence of the devices is dominated by carrier leakage to the X
minima of the Al$_{0.35}$Ga$_{0.65}$As$_{0.03}$Sb$_{0.97}$ barrier layers
accounting for up to 43% of the threshold current at room temperature.
Improvement in device performance may be possible through refinements in the
CQW design, while carrier confinement may be improved by optimization of the
barrier layer composition. This investigation provides valuable design insights
for the monolithic integration of GaSb-based lasers on silicon.
