What is an optical semiconductor?

optical semiconductor

What is the “optical” in optical semiconductor?

Light is classified in the same category as X-rays used at hospitals and electric waves used for TV and mobile phones: they are all electromagnetic waves. The difference between light and electric waves is in there wavelengths, as shown in the figure below.

What is the “optical” in optical semiconductor?

What is the “semiconductor” in optical semiconductor device?

Semiconductors have properties that place them between conductors and insulators.
Materials are classified as conductors, semiconductors, or insulators, according to their electrical conductivity.
Typical conductors are gold, silver, and copper. Materials like rubber, glass, ceramic, and plastic are classified as insulators.
Typical semiconductors are silicon, germanium, and furthermore compound semiconductors (GaAs, GaP, GaN and InP), with silicon the most widely used. Semiconductor transistors support the foundation of modern society, and integrated circuits (ICs) made up of millions of transistors are semiconductor products.

Next to oxygen, silicon is the most abundant element in the earth’s crust, and is always found in sand and stone in nature. Germanium, silicon, and compound semiconductor elements are generally refined from raw ore.

What is the “semiconductor” in optical semiconductor device?

What is the “device” in optical semiconductor device?

A device is a piece of equipment used for a particular purpose. Optical semiconductor devices have a minutely detailed structure that allows them to convert electricity into light or light into electricity.

An Optical Semiconductor (Light Emitting Element) That Converts Electric Current into Light

LED Lighting, traffic lights, displays, backlights for electronic devices, etc.
Laser diodes Writing of DVDs, optical fiber communication, 3D sensors, etc.
Infrared LED TV remote controls, security cameras, vehicle cameras, etc.
LED Lighting, traffic lights, displays, backlights for electronic devices, etc.
Laser diodes Writing of DVDs, optical fiber communication, 3D sensors, etc.
Infrared LED TV remote controls, security cameras, vehicle cameras, etc.

Optical Semiconductors (Light Receiving Element) That Convert Light into Electric Current

Photodiodes Camera exposure meters, optical communication systems, spectroscopes, night vision devices, etc.
Phototransistors Used for a wide range of applications including automatic doors, cameras, smartphones, photoelectric sensors, etc.
Photodiodes Camera exposure meters, optical communication systems, spectroscopes, night vision devices, etc.
Phototransistors Used for a wide range of applications including automatic doors, cameras, smartphones, photoelectric sensors, etc.

What is an optical semiconductor?

Optical semiconductor devices are divided into two major groups: luminescent devices (light-emitting diodes and laser diodes), and light-receiving devices (solar cells and photo-detectors). The wavelengths of the light depend on the optical semiconductor materials used.

Deep UV AlGaN / GaN on Sapphire
Violet, Blue InGaN / GaN on Sapphire
Green GaP on GaP
Yellow AlInGaP on GaAs
Red GaAlAs on GaAs
Infrared GaAlAs on GaAs
Near infrared InGaAs on InP (for Photo-detector)
InGaAsP on InP (for LED)
Deep UV AlGaN / GaN on Sapphire
Violet, Blue InGaN / GaN on Sapphire
Green GaP on GaP
Yellow AlInGaP on GaAs
Red GaAlAs on GaAs
Infrared GaAlAs on GaAs
Near infrared InGaAs on InP (for Photo-detector)
InGaAsP on InP (for LED)

While some materials are made of a single element such as Si and Ge, other materials, like those shown above, are made of several elements and are called compound semiconductors.

What is a compound semiconductor?

While Si and Ge are mainly used for photo-detectors due to their extremely low luminous efficiency, compound semiconductors are used for LEDs and laser diodes due to their high luminous efficiency. Furthermore, compound semiconductors are suitable for high-speed operation and are used in high-speed photodiodes for optical communications.

Combination of Compound Semiconductors as Seen from the periodic table

B C N
AI Si P
Zn Ga Ge As Se
Cd In Sn Sb Te

A wide range of applications for optical semiconductors

Wireless remote controllers for products like TVs and air conditioners transmit and receive information using infrared rays. CD and DVD called as optical media are used to write and read information on a storage medium by light. Electrical equipment using light in the way above is in everywhere we look.

As you know, incandescent and fluorescent lamps, which are used to be the dominant lighting, are recently and rapidly being replaced by light-emitting diodes, or LEDs.
Same movements are very often seen for traffic signals, as well as in flashlights and car headlights. These LEDs are one type of optical semiconductor device.