We present a 1.65 μm GaSb/AlGaSb quantum-well (QW) laser operating at room temperature, grown buffer-free on a GaAs substrate. The enabling technology in this device is a layer of interfacial misfit dislocations (IMF) that completely relieve the strain between the GaAs substrate and the GaSb epi-layer without the use of thick metamorphic buffers. The IMF array is localized to the GaAs/GaSb interface, allowing current to pass through electrically pumped devices without the detrimental effects of threading dislocations that result in large voltage drops and non-radiative recombination. This growth technology provides an effective way of integrating III-Sb based devices such as IR-lasers, detectors and transistors with a higher quality and more scalable substrate such as GaAs.