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 heating a substrate containing a semiconductor surface in the presence of a nitrogenous material thereby to form a nitride interface layer of sufficient thickness to passivate said semiconductor surface; cooling the semiconductor surface; subsequently depositing a metal layer over the interface layer using a thermally evaporated 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 the nitrogenous material comprises a gas.
3. The method of claim 2 , wherein the gas comprises ammonia.
4. The method of claim 1 , wherein the substrate contains an exposed silicon surface and is annealed at a temperature between approximately 300° C. and approximately 750° C.
5. The method of claim 1 , the heating is performed in a heating chamber and prior to the heating, pulling a vacuum of less than approximately one millionth of a Torr in the heating chamber, and then heating the substrate in the heating chamber.
6. The method of claim 1 , wherein the substrate is heated to a temperature between approximately 900° C. and approximately 1000° C. in an inert ambient.
7. The method of claim 1 , wherein the semiconductor surface is exposed to a pulse of ammonia for a time period between approximately 0.5 seconds and approximately 5 seconds.