madphdstudent said:Suppose we have a p-type material and metal contacts deposited taking the work function of a metal and semiconductor into account. At room temperature (depending on the doping level) they might now show linear IV curve (non-ohmic behavior). How does annealing at higher temperature improves the ohmic contacts and eventually become ohmic? Is there a way to calculate at which temperature to expect the transition?
Anything that has been exposed to atmosphere will have adsorbed layers of adventitious carbon, water etc. on the surface which is typically insulating. By annealing after deposition you effectively remove some of this carbon (this is most obvious in an ultra-high vaccum.) The temperature is a function of the bond strength between the adsorbed species and the material.madphdstudent said:Thanks for your reply zz. That definitely is true. Here materials does not matter here since I am asking the temperature dependence of the barrier potential right? Only numeric here would be work functions (work function of a metal> work function of the semiconductor) - meaning they should make it ohmic. But If that would help let's suppose that the contact metal is silver and semiconductor is p-type silicon. How does it become ohmic with temperature and how they remain ohmic is my question.
Some ohmic contacts do rely on formation of metal-semiconductor phases (e.g. formation of Ni-Ga-O phase in case of Ni/Au contact on p-GaN). So it's important to identify the material you are interested in.madphdstudent said:Thanks for your reply zz. That definitely is true. Here materials does not matter here since I am asking the temperature dependence of the barrier potential right? Only numeric here would be work functions (work function of a metal> work function of the semiconductor) - meaning they should make it ohmic. But If that would help let's suppose that the contact metal is silver and semiconductor is p-type silicon. How does it become ohmic with temperature and how they remain ohmic is my question.
Annealing is a heat treatment process that involves heating a material to a specific temperature and then cooling it slowly. This process helps to remove defects and impurities in the material, allowing for better electrical conductivity and improved ohmic contact.
Annealing can be beneficial for various types of materials, including metals, semiconductors, and even polymers. It is commonly used in the production of electronic devices such as transistors and diodes, where ohmic contact is crucial for proper functioning.
During the annealing process, the high temperature causes the atoms on the surface of the material to diffuse, rearrange, and form new regions with enhanced electrical properties. This results in a smoother and more uniform surface, which improves the contact between the material and the electrode.
No, there are other techniques that can be used to improve ohmic contact, such as surface cleaning, chemical treatments, and ion implantation. However, annealing is often the most effective method as it can improve the electrical properties of the entire material, rather than just the surface.
One potential drawback of annealing is that it can alter the properties of the material, particularly its mechanical strength. This can be a concern for certain applications where the material needs to maintain its original properties. Additionally, annealing can be a time-consuming and expensive process, especially for large-scale production.