Extrinsic semiconductor n- type and p- type Semiconducter r.pptx

extrinsic semiconductor n-type and p-type semiconductor

1. SEMICONDUCTOR (EXTRINSIC) Central University of Kerala Submitted to- Dr. Bini George Department of Chemistry Submitted by- Rojalin Pradhan (2201105022) Divya Dhakar (2201105011) M.Sc. Chemistry 2 nd Year

2. What is EXTRINSIC semiconductor ? It is a type of semiconductor material that has been intentionally modified by adding a small amount of specific impurity atoms to its crystal lattice. This process is called “ doping”. To make its better conductivity. Als o called doped semiconductor . Extrinsic semiconductors are typically used in electronic devices and integrated circuits. Based on impurities added extrinsic semiconductor are mainly two types: 1. N-Type 2. P-Type

3. N-TYPE N-type semiconductor is formed when  group V  elements are doped to an intrinsic semiconductor. Elements like arsenic, antimony, bismuth etc. are doped in order to have n-type semiconductor hence it produces an additional electron thus also termed as  donor atom . E lectrons act as majority charge carriers while holes are minority charge carriers. Si - [Ne] 3s² 3p² P - [Ne] 3s² 3p³ Number of e - >> Number of holes

4. I t is clear that the existence of the Fermi level is near the conduction band. We can see that the small energy difference exists between donor energy level and the conduction band. So, less energy is needed by the electrons to reach the conduction band. “P” donate e- and it becomes P + ; extra e- and the positive charge of “P” neutralizes; thus it is a neutral semiconductor.

5. P-TYPE When an intrinsic semiconductor is doped with group III elements of periodic table like  boron, gallium, aluminium   etc. that these are known as the p-type extrinsic semiconductor. As elements like boron, gallium, indium etc. are doped to form p-type semiconductor thus it produces an additional hole hence also known as   acceptor atom .  P -type semiconductor holes are the majority carriers while electrons are minority charge carrier. Al - [Ne] 3s² 3p¹ Si - [Ne] 3s² 3p² Number of e - << Number of holes

6. Fermi level is present near the valence band. As it is clear from the above figure that there exists a very small energy difference between valence band and the acceptor energy level. Thus, electrons easily drift to acceptor energy level creating a vacancy of electrons. Hence, producing holes in the valence band . Al accept e - and it becomes Al - so hole and this negative charge neutralizes so it is a neutral semiconductor.

7. USES AND APPLICATIONS: Used in the manufacturing of transistors like  NPN  type,  PNP  type, and  Bipolar junction transistors  (BJT). Manufacturing of  solar cells ,  light emitting diodes  and other photovoltaic devices. To make laser beams.

8. CONCLUSION So, from the above discussion, we can conclude that a p-type semiconductor is abbreviated so because these are positive semiconductors due to presence of extra holes. Whereas, n-type semiconductors are termed as negative semiconductors because of the presence of extra electrons. Thankyou