Method for depinning the Fermi level of a semiconductor at an electrical junction and devices incorporating such junctions
An electrical device in which an interface layer is disposed between and in contact with a metal and a Si-based semiconductor, the interface layer being of a thickness effective to depin of the Fermi level of the semiconductor while still permitting current to flow between the metal and the semiconductor. The interface layer may include a layer of a passivating material (e.g., made from nitrogen, oxygen, oxynitride, arsenic, hydrogen and/or fluorine) and sometimes also includes a separation layer. In some cases, the interface layer may be a monolayer of a semiconductor passivating material. The interface layer thickness corresponds to a minimum specific contact resistance of less than or equal to 10 Ω-μm 2 or even less than or equal to 1 Ω-μm 2 for the electrical device.
1. A method, comprising cleaning a semiconductor substrate with a cleaning solution to form a cleaned substrate; immersing, for a period of time between several seconds and approximately five (5) minutes, the cleaned substrate in a solution containing hydrogen and fluorine ions of between approximately 1%-50% by weight; removing the substrate from the solution and blow-drying the substrate with nitrogen, thereby forming an interface layer containing hydrogen and fluorine on the semiconductor substrate, said interface layer being of sufficient thickness to passivate a surface of said semiconductor substrate in a vicinity of said interface layer; subsequently depositing a metal layer over the interface layer through thermal evaporation of a source, thereby forming a junction having a metal layer disposed over the interface layer disposed over the semiconductor, said junction having a specific contact resistance of less than or equal to approximately 1000 Ω-μm 2 .
2. The method of claim 1 , wherein following removal of the substrate from the solution and prior to blow-drying the substrate with nitrogen, rinsing the substrate in deionized water for less than 30 sec.