Our course on p-n junction and metal-semiconductor contact consists of three parts: p-n junction, metal-semiconductor contact, and optoelectronic devices based on this basic device structure. In the p-n junction part, we will discuss what p-n junction is, and what their energy band diagram looks like, and how this energy band structure leads to the unique properties, especially the capacitance, voltage and current voltage characteristics of a p-n junction. We will also discuss junction breakdown, which refers to the phenomenon of current increasing rapidly under a very large reverse bias. We will discuss two different mechanisms that could lead to junction breakdown, and we will discuss the similarities and differences between these two mechanisms. Finally, we will discuss heterojunction, which is a p-n junction made of two different materials. Because of the difference in energy band structure between the two materials, we have additional degree of freedom with which we can control the electrical properties of p-n junction device, and we will see how we can incorporate heterojunction to improve the performance of simple p-n junction device. Next, we will discuss metal-semiconductor contact. There are two types of metal-semiconductor contact: Schottky and Ohmic. Schottky contact is a rectifying contacts and their current characteristics are quite similar to a p-n junction. However, the current mechanism responsible for this current characteristics are fundamentally different. We will discuss what is the mechanism behind these operations of Schottky contact and how they lead to the similar and yet different current behavior in Schottky contact compared to the p-n junction device. Ohmic contact is a metal-semiconductor contact that is non-rectifying. This is a contact that is required for almost all of semiconductor devices, and it is of fundamental importance. We will discuss two different ways to produce Ohmic contact, and we will present a theoretical description that could provide the rigorous description of the behavior of this Ohmic contact device. Finally, we will discuss the defects that may be present at the interface between metal and semiconductor and how these defects may impact the performance of the semiconductor device. Finally, we will discuss optoelectronic devices. We will start with light-emitting diode as shown here. Light-emitting diode has been used in a variety of applications, but most notably, in the past decade or so, light-emitting diode has become a mainstream technology in the multibillion dollar lighting industry. So, we will discuss the basic operation of LED and how they may be used for general lighting application. Then we will discuss laser diode and how semiconductor is an excellent material to produce laser by providing far greater gain and then any other material, and also allows fast switching. This is why laser diode is so commonly used especially in communications, but also in many other applications. Next, we will discuss photodiode and how semiconductor device can be used to very efficiently detect incoming light. Finally, we will discuss solar cell and how this semiconductor device can be used to harvest sunlight and produce electrical power.