US Patent 9852938 Passivated germanium-on-insulator lateral bipolar transistors

After forming an epitaxial germanium layer over a germanium-on-insulator substrate including an insulator layer and a doped germanium layer overlying the insulator layer, the doped germanium layer is selectively removed and a passivation layer is formed within a space between the epitaxial germanium layer and the insulator layer that is formed by removal of the doped germanium layer. A lateral bipolar transistor is subsequently formed in the epitaxial germanium layer.