Before discussing the construction and working of semiconductor laser, let us discuss the review of semiconductors as it will be necessary for you to write the basics of semiconductors in case of exams:
A semiconductor is a material whose conductivity lies between those of conductor and insulator. Semiconductors are of two types:
a) Intrinsic semiconductors or pure semiconductors
b) Extrinsic semiconductors or doped semiconductors
Extrinsic semiconductors are further classified into two types depending upon the type of majority carriers:
i) n-type semiconductors where electrons are majority carriers.
ii) p- type semiconductors where holes are majority carriers.
When a p-type semiconductor and a n- type semiconductor is joined by special techniques, there will be flow of electrons from n side to p side and flow of holes from p side to n side. After some time, an electric field will be created which will oppose this flow and flow stops. Thus, there will be formation of depletion region. This region is called so because it is depleted from charge carriers.
Note: In next article I will explain the construction of semiconductor laser. In case of any problem in this article or any other physics article, kindly post in the comment section.
Reference: This article is referred from my authored book “optics and lasers” having ISBN 978-81-272-2948-2