What are semiconductors?

A semiconductor is a material (commonly a solid chemical element or compound) with distinct electrical properties: in some cases it will conduct electricity, but not in others. Thus, control of electrical current is enabled. A semiconductor’s conductance varies depending on the current or voltage applied to a control electrode, or on the intensity of irradiation by infrared (IR), visible light, ultraviolet (UV), or X rays.

Graphenea/ICFO graphene wafer

Semiconductors can be found at the heart of modern electronics. Some examples include microprocessor chips and transistors, and virtually any device that is computerized or uses radio waves relies on semiconductors. Nowadays, the most commercially important semiconductor is silicon, although many others are also in use.

What is graphene?

Graphene is a one-atom-thick layer of carbon atoms arranged in a hexagonal lattice. It is the building-block of Graphite (which is used, among others things, in pencil tips), but graphene is a remarkable substance on its own - with a multitude of astonishing properties which repeatedly earn it the title "wonder material".

Graphene is the thinnest material known to man at one atom thick, and also incredibly strong - about 200 times stronger than steel. On top of that, graphene is an excellent conductor of heat and electricity and has interesting light absorption abilities. Graphene has potential to revolutionize many applications, among these are solar cells, batteries, sensors and more.



Graphene as a semiconductor

Semiconductors are defined by their band gap: the energy required to excite an electron stuck in the valence band, where it cannot conduct electricity, to the conduction band, where it can. The band gap needs to be large enough so that there is a clear contrast between a transistor’s on and off states, and so that it can process information without generating errors.

Among graphene's superlative properties is exceptional electrical conductivity. This property makes the material attractive for many applications, but it is problematic for use as a semiconductor. For that, graphene would need a bandgap (which it normally lacks), or in other words to behave not just as a conductor but to also have an insulator mode.

Scientists have found various methods to introduce a bandgap to graphene. By fabricating graphene in specific shapes (like ribbons), by using certain growth methods paired with specific materials, by using graphene's morphological structure (namely wrinkles), by doping the material and more. Other 2D materials can be used instead or together with graphene, that have an inherent bandgap. These materials may prove to be an easier path towards next-gen semiconductor based devices.