We are trying to purchase some silicon wafers to make nanofluidic devices (etching around 10 nm channels onto the surface of the wafer). I see a lot of opinions on your website regarding the type dopant etc. and I am not very sure which one is best suited for our lab purpose. So I have some questions for you:
What is the difference between doped and undoped wafer? what does P and N mean? How does they affect the wafer?
What is the difference between As, B, P dopant?
What does orientation <100> <110> <111> mean?
What is the difference between the grades? (mech, test and prime)?
UniversityWafer, Inc. Replied:
Most crystals are grown with dopant added to the silicon. If wafers are doped with Boron making them p-type extrinsic semiconductor or Phosphorus, Arsenic or Antimony making them n-type extrinsic semiconductor.
As and P make wafers b-type, B makes the wafers p-type.
See below for some of the important extrinsic semiconductor topics
Intrinsic Semiconductor Important Terms
What is the Conductivity of an Extrinsic Semiconductor?
Conductivity of an extrinsic semiconductor can be calculated using the p-type calculator, by finding the Acceptor Concentration (AC) and the Mobility of Electron (ME). The n-type calculation uses the Mobility of Electron and valance band hole, which are components of the conduction band and participate in electrical conduction. The n-type conductivity of extrinsic semiconductors is denoted by the sn symbol.
Differences Between Intrinsic and Extrinsic Semiconductors
The difference between an intrinsic and an extrinsic semiconductor lies in the amount of doping and charge carriers. A semiconductor that is intrinsic is completely pure, whereas one that is extrinsic has impurities and doping agents. This means that a semiconductor that is intrinsic is less dense than one that is extrinsic. Here are some examples of intrinsic semiconductors.
An intrinsic semiconductor is completely pure. It is a semiconductor that contains no impurities and exhibits negligible conductivity at room temperature. The conductivity of an intrinsic semiconductor is determined by the material's properties, not by the number of impurities. The number of electrons in the conduction band equals the number of holes in the valence band. In addition, the number of holes in the crystal structure will not affect the amount of charge carriers that flow.
Extrinsic semiconductors, on the other hand, have impurities. They have four electrons that are covalently bonded, while one free electron. This causes them to be more conductive than expected. Thankfully, modern technology allows us to purify semiconductors and increase their electrical conductivity. But even with the purification process, it's important to know the differences between extrinsic and intrinsic semiconductors.
An intrinsic semiconductor is a pure semiconductor, while an extrinsic semiconductor is doped with impurities. The extrinsic semiconductor is doped with impurities and is classified as either p-type or n-type. This distinction can be made clear by the difference in temperature and impurity concentrations between the two types of semiconductors. So, which is better?
While an extrinsic semiconductor is more expensive, it has better electrical conductivity. This type is used in many applications where a pure semiconductor does not conduct a current. But the energy gap between extrinsic and intrinsic semiconductors is larger. The difference between extrinsic and intrinsic semiconductors is quite significant. If you're looking for a semiconductor that performs well in electronic circuits, you've come to the right place.
In the process of semiconductor production, impurities are added to the intrinsic semiconductor. These impurities enhance the semiconductor's conductivity. Impurities can either be pentavalent (five electrons in the valence shell) or trivalent (three electrons). The pentavalent impurities are used to make an N-type semiconductor. They can also be doped into intrinsic semiconductors by adding metals to them.
Mechanisms that govern electrical conductivity in a semiconductor
A semiconductor can conduct electricity under preferable conditions and control the conductivity of the current. Electrons move in the material from lower energy states (valence band) to higher-energy states (conduction band). These electrons are called charge carriers and have an equal number of occupied and unoccupied energy states. As a result, their mobility decreases as the temperature increases. The following discussion provides an overview of the mechanisms that govern electrical conductivity in an extrinsic semiconductor.
Free charge carriers drift through the material and are generated by thermal excitation of electrons. This process leads to a rapid rise in conductivity. The simple dependence of se on temperature is given by the equation (58) where DE is the activation energy of the electrons. The intrinsic semiconductors include molecular and pure-to-lightly doped inorganic semiconductors, polymeric semiconductors such as poly(sulfur nitride), and undoped conjugated chain polymers such as acetylene.
The resistance of an extrinsic semiconductor is proportional to its cross-sectional area (A), and inversely proportional to its length. In a cubic cube, A=1 m2 contains perfectly conductive contacts and a resistance equal to Om. The electrical conductivity is then measured in ohm-meters. A unit of electrical resistance is an ohm.
The maximum conductivity is governed by the carrier-carrier interactions. The carrier-carrier interactions dominate the conductivity if the Coulomb gap width is greater than the energetic disorder. The carrier-carrier interactions are as general as Coulomb attraction, and the results of these experiments suggest that a combination of both processes is necessary for a material to achieve a high electrical conductivity.
Electron transfer between carrier and electron is crucial for the electric conductivity of the extrinsic semiconductor. If the two carriers are separated by an energy barrier, then the transfer will be incomplete. This causes a gap between carrier and electron and is therefore called the Coulomb gap. The energy gap between two carriers is the result of an imbalance in electron and hole masses. The gap between the two states is related to the electron-hole mass and valence band energy.
Charge carriers can be introduced into an organic semiconductor through doping, which introduces opposite-charged dopants into a semiconductor. This introduces a number of charge carriers to the material, and the mobility of the carriers depends on the rate at which these carriers can move. Doping also increases the mobility of carriers. Dopant-carrier interactions are a key strategy in the development of high-conductivity organic semiconductors.
Electron transport in an extrinsic semiconductor occurs by the passage of full atomic species. Ions move through the pores and carry a charge. In contrast, ionic liquids are electrically insulators while dissolved salts are electrically conducting. The resistance of biological membranes is controlled by ion channels that select specific ions. This is the mechanism by which cell membranes carry currents.
Effects of an electric field on the conductivity of an extrinsic semiconductor
The electrical properties of an extrinsic semiconductor are determined by the concentrations of two types of impurities: acceptor and donor. During the conduction of an electrical current, electrons in the acceptor impurity are promoted to the acceptor level by an electric field. The electrons then jump to the hole and carry the electrical current. For extrinsic semiconductors, the hole is the majority charge carrier.
When a semiconductor is placed in an electric field, the free electrons and holes are accelerated to the conduction band. They move through the crystal to produce an electrical current. The number of carriers per unit volume, as well as their velocities and mobilities, determine the electrical conductivity of the material. A semiconductor has an equal number of both holes and electrons, but their mobility and velocities in an electric field are different.
Electrical conductivity is affected by temperature, impurities, and band gap energy. An extrinsic semiconductor is made of materials with very high purity, which usually means a total impurity content of 10-7 at%. During processing, large numbers of charge carriers are formed, known as intrinsic carriers. The intrinsic carriers are always larger than the holes, due to enhanced thermal scattering. Because the intrinsic carriers increase with increasing temperature, they exhibit high room-temperature electrical conductivity.
The electrical resistance of an extrinsic semiconductor depends on the temperature and impurity concentration, which are proportional to each other. The electrical resistance of the material can be increased by cold working or adding a second phase, which increases its strength. A common extrinsic semiconductor is silicon, which has a room-temperature electrical resistance of 0.10-60 O-cm, whereas an extrinsic semiconductor has a resistance of tens to one order of magnitude smaller than an insulator.
When temperatures increase in the extrinsic region, the effect of ionized impurity scattering disappears. Electrons in the valence band become displaced from the valence band, increasing the conduction band and increasing hole mobility. The conductivity increases with increasing temperature. If this happens, the extrinsic semiconductor becomes an intrinsic one.
The electrons below the conduction band occupy discrete energy levels. They may be a positive or negative charge carrier in an electric field. If they are free, they will migrate into empty energy states above Fermi energy (Ef). The electric field can excite a large number of electrons into conducting states. These electrons are not present in an extrinsic semiconductor.
The conductivity of an extrinsic material depends on the type of impurity. An n-type semiconductor contains more electrons than a p-type. It conducts holes in the valence band. A p-type semiconductor is a combination of electrons and holes. Its conductivity increases as the electron concentration in the semiconductor increases.
What are Differences Between Intrinsic and Extrinsic Semiconductors?
Intrinsic semiconductors are less conductible than extrinsic semiconductors. Hence, it's important to know the difference between them. Extrinsic semiconductors are more active and have a higher conductivity. They are therefore preferred by most people.
When a semiconductor material is in its pure form, it is known as an intrinsic semiconductor. In contrast, extrinsic semiconductors are contaminated with one or more elements, called impurities. This affects their conductivity levels, which vary with temperature and concentration.
Intrinsic semiconductors are made from elements from group IV, such as silicon and germanium. These materials contain four valence electrons and require only a small amount of energy to break their covalent bond. Because of their crystalline structures, these atoms are bonded to their neighboring atoms through shared electrons.
The difference between intrinsic and extrinsic semiconductor properties is in the amount of electrons and holes. In the case of intrinsic semiconductors, the density of electrons is equal to the density of holes, whereas in extrinsic semiconductors, the ratio of holes to electrons is different. This means that in extrinsic semiconductors, more electrons are present than holes, making them more conductive.
Electrical conductivity is a property that semiconductors share, but it depends on their structure and their composition. For example, silicon is an intrinsic semiconductor and contains equal amounts of electrons and holes. The extrinsic semiconductor, on the other hand, is created by mixing a material with an impurity.
As a result of their differences, it's important to understand the difference between extrinsic and intrinsic semiconductors. Intrinsic semiconductors are pure, while extrinsic ones are impure. They are formed when a semiconductor material is doped with trace elements, such as trivalent iron.
Intrinsic motivation involves enjoyment of an activity, while extrinsic motivation is driven by rewards from others. Whether it's winning a competition or setting a personal goal, intrinsic motivation can help you get the most out of your training. This can increase your chances of winning the competition or beating your personal best.
Methods of determining intrinsic motivation
There are several approaches to determining intrinsic motivation, each focusing on a different component of the motivation process. The first approach, known as the information theoretic approach, focuses on the explicit reward computation mechanism. The second approach, based on measures of competence, describes the general architecture of motivation, whereas the third approach uses mathematical/morphological properties of the sensorimotor flow independent of the internal cognitive system.
Information theoretic measures of motivation and the capacity to predict situations are often used to determine intrinsic motivation. For example, the drive for novelty is an example of an adaptive motivation that can change over time. The person may remember a situation that once seemed novel, but will no longer find it as appealing after a while. This can have an effect on behavior and decision making.
Another example of intrinsic motivation is when children do their homework for fun. They may be motivated by the discovery of new knowledge, or they may find the math problems to be enjoyable. In this case, the intrinsic motivation is greater than the extrinsic motivation. A child may be motivated to do homework for fun because they enjoy solving math problems.
In addition to the intrinsic motivation, there is the general motivation. This type of motivation is the most common in humans. People engage in activities to satisfy their curiosity, and these activities are termed intrinsic by psychologists. This kind of motivation is a fundamental driver of sensory and cognitive development. There is a vast literature describing the importance of intrinsic motivation in humans. The main difference between the two types of motivation is the source of motivation.
Mechanism of extrinsic rewards
The extrinsic reward is a type of reward that comes from outside of the person performing the task. Such rewards can come from a variety of sources, including tangible rewards such as a trophy for winning a race, a badge that you earned by doing a job well, or even money. Generally, these rewards come from something that the person doing the activity has done well.
As a result of this extrinsic reward, the intrinsic semiconductor is able to absorb excess electrons from other materials, which increases its capacity to absorb electrons. As a result, the semiconductor becomes an n-type semiconductor. The acceptor impurity atoms have fewer valence electrons than the intrinsic semiconductor, and thus provide the excess holes.
Methods of determining extrinsic motivation
Intrinsic motivation is a type of motivation that does not depend on any external factors. This type of motivation is difficult to prove and corroborate because it is possible for individuals to engage in a behavior even when there is no external reward. However, some psychologists reject the concept of intrinsic motivation and insist that human motivations cannot be categorized. For example, professor Steven Reiss at Ohio State University says that the human motivation is not deterministic, but rather a complex set of interrelated factors that must be studied to understand human motivations.