A method of forming the heterojunction bipolar transistor that includes providing a stack of a base layer, an extrinsic base layer, a first metal containing layer, and a dielectric cap layer. The dielectric cap layer and the first metal containing layer may be etched to provide a base contact and a dielectric cap. Exposed portions of the base layer may be etched selectively to the dielectric cap. A remaining portion of the base layer provides the base region. A hydrogenated silicon containing layer may be deposited with a low temperature deposition method. At least a portion of the hydrogenated silicon containing layer is formed on at least sidewalls of the base region. A second metal containing layer may be formed on the hydrogenated silicon containing layer. The second metal containing and the hydrogenated silicon containing layer may be etched to provide an emitter region and a collector region.