An exemplary device includes a channel layer, a first epitaxial source/drain feature, and a second epitaxial source/drain feature disposed over a substrate. The channel layer is disposed between the first epitaxial source/drain feature and the second epitaxial source/drain feature. A metal gate is disposed between the first epitaxial source/drain feature and the second epitaxial source/drain feature. The metal gate is disposed over and physically contacts at least two sides of the channel layer. A source/drain contact is disposed over the first epitaxial source/drain feature. A doped crystalline semiconductor layer, such as a gallium-doped crystalline germanium layer, is disposed between the first epitaxial source/drain feature and the source/drain contact. The doped crystalline semiconductor layer is disposed over and physically contacts at least two sides of the first epitaxial source/drain feature. In some embodiments, the doped crystalline semiconductor layer has a contact resistivity that is less than about 1×10−9 Ω-cm2.