Lateral quantum dot
Encyclopedia
A lateral quantum dot is a type of quantum dot
made by imposing a small area
of decreased potential
in the two dimensional electron gas (2DEG
) by means of electrical gates such that electrons or electron hole
s are confined in the 2DEG
plane. The particles are confined in one dimension
laterally where they are free to move in the plane of the 2DEG
. Once the potential is applied, it is energetically favorable for a certain number of electron
s (or holes) to remain confined in a certain area of the 2DEG causing the remaining two-dimensional freedom to be removed and the three dimensional confinement
of the electron
s or holes. The 2DEG is confined between two semiconductor
sheets such as InAs
and GaAs
. The fabrication
process for a lateral dot is much different than that for a self-assembled quantum dot
.
where you can roll a ping pong ball all around it and across it. However, when a rather heavy object is placed in the centre, the ping pong ball rolls towards in the centre and becomes trapped. The electrical gate (heavy object) is what is cause the lowering of the potential (trampoline surface). The particle (ping pong ball) cannot go through the floor, through the ceiling or to the sides of the trampoline; thus it is confined!
Quantum dot
A quantum dot is a portion of matter whose excitons are confined in all three spatial dimensions. Consequently, such materials have electronic properties intermediate between those of bulk semiconductors and those of discrete molecules. They were discovered at the beginning of the 1980s by Alexei...
made by imposing a small area
Area
Area is a quantity that expresses the extent of a two-dimensional surface or shape in the plane. Area can be understood as the amount of material with a given thickness that would be necessary to fashion a model of the shape, or the amount of paint necessary to cover the surface with a single coat...
of decreased potential
Potential
*In linguistics, the potential mood*The mathematical study of potentials is known as potential theory; it is the study of harmonic functions on manifolds...
in the two dimensional electron gas (2DEG
2DEG
A two-dimensional electron gas is a gas of electrons free to move in two dimensions, but tightly confined in the third. This tight confinement leads to quantized energy levels for motion in that direction, which can then be ignored for most problems. Thus the electrons appear to be a 2D sheet...
) by means of electrical gates such that electrons or electron hole
Electron hole
An electron hole is the conceptual and mathematical opposite of an electron, useful in the study of physics, chemistry, and electrical engineering. The concept describes the lack of an electron at a position where one could exist in an atom or atomic lattice...
s are confined in the 2DEG
2DEG
A two-dimensional electron gas is a gas of electrons free to move in two dimensions, but tightly confined in the third. This tight confinement leads to quantized energy levels for motion in that direction, which can then be ignored for most problems. Thus the electrons appear to be a 2D sheet...
plane. The particles are confined in one dimension
Dimension
In physics and mathematics, the dimension of a space or object is informally defined as the minimum number of coordinates needed to specify any point within it. Thus a line has a dimension of one because only one coordinate is needed to specify a point on it...
laterally where they are free to move in the plane of the 2DEG
2DEG
A two-dimensional electron gas is a gas of electrons free to move in two dimensions, but tightly confined in the third. This tight confinement leads to quantized energy levels for motion in that direction, which can then be ignored for most problems. Thus the electrons appear to be a 2D sheet...
. Once the potential is applied, it is energetically favorable for a certain number of electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s (or holes) to remain confined in a certain area of the 2DEG causing the remaining two-dimensional freedom to be removed and the three dimensional confinement
Confinement
Confinement may refer to either* Civil confinement for psychiatric patients* Color confinement, the physical principle explaining the non-observation of color charged particles like free quarks* Solitary confinement, a strict form of imprisonment...
of the electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s or holes. The 2DEG is confined between two semiconductor
Semiconductor
A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...
sheets such as InAs
Indium(III) arsenide
Indium arsenide, InAs, or indium monoarsenide, is a semiconductor material, a semiconductor composed of indium and arsenic. It has the appearance of grey cubic crystals with a melting point of 942 °C....
and GaAs
Gaas
Gaas is a commune in the Landes department in Aquitaine in south-western France....
. The fabrication
Microfabrication
Microfabrication is the term that describes processes of fabrication of miniature structures, of micrometre sizes and smaller. Historically the earliest microfabrication processes were used for integrated circuit fabrication, also known as "semiconductor manufacturing" or "semiconductor device...
process for a lateral dot is much different than that for a self-assembled quantum dot
Quantum dot
A quantum dot is a portion of matter whose excitons are confined in all three spatial dimensions. Consequently, such materials have electronic properties intermediate between those of bulk semiconductors and those of discrete molecules. They were discovered at the beginning of the 1980s by Alexei...
.
Simplified Conceptualization
Think of it as inside a room with really low ceilings with a trampolineTrampoline
A trampoline is a device consisting of a piece of taut, strong fabric stretched over a steel frame using many coiled springs. People bounce on trampolines for recreational and competitive purposes....
where you can roll a ping pong ball all around it and across it. However, when a rather heavy object is placed in the centre, the ping pong ball rolls towards in the centre and becomes trapped. The electrical gate (heavy object) is what is cause the lowering of the potential (trampoline surface). The particle (ping pong ball) cannot go through the floor, through the ceiling or to the sides of the trampoline; thus it is confined!