Predict whether each of the following elements will act as a donor or an acceptor when added to the indicated semiconducting material. Assume that the impurity elements are substitutional. $$ \begin{array}{lc} \hline \text { Impurity } & \text { Semiconductor } \\ \hline \text { N } & \text { Si } \\ \hline \text { B } & \text { Ge } \\ \hline \text { S } & \text { InSb } \\ \hline \text { In } & \text { CdS } \\ \hline \text { As } & \text { ZnTe } \\ \hline \end{array} $$

In semiconductors, impurities can dramatically change the conductivity of the material. These impurities are classified as either donor or acceptor impurities based on their interaction with the semiconductor's lattice. Donor impurities, typically elements from Group V of the periodic table, have one more valence electron than the semiconductor. When these elements are added to a semiconductor, the extra electron becomes free to conduct electricity. Conversely, acceptor impurities are usually from Group III and have one less valence electron compared to the semiconductor. These impurities create holes by accepting an electron, which also contributes to the ability to conduct electricity.

Understanding these concepts is essential as it allows us to predict the behavior of a semiconductor with added impurities. For instance, nitrogen (N) becomes a donor when added to silicon (Si) as it introduces additional free electrons, turning Si into an n-type material. These interactions are crucial for designing electronic devices, as they determine the flow of current and the behavior of the device.

Semiconductors are the backbone of modern electronics, and their conductivity can be controlled by doping with impurities, which are intentionally introduced to its crystal structure. Two resulting types of semiconductors are n-type and p-type materials. N-type materials contain donor impurities that add extra electrons to the conduction band, increasing the number of charge carriers. In contrast, p-type materials are created by introducing acceptor impurities that create holes, or the absence of an electron, which act as positive charge carriers.

The type of doped semiconductor is crucial in the formation of p-n junctions, which are the foundation of diodes and transistors. By understanding the doped n-type and p-type materials, students can appreciate the design and functionality of a wide variety of electronic components.

Valence electrons are the outermost electrons of an atom and are vital in the understanding of semiconductor behavior. In semiconductors, these electrons are on the cusp of the conduction band and therefore can become mobile and contribute to electrical conductivity. Silicon and germanium, both used extensively in semiconductors, each have four valence electrons. In a pure, intrinsic state, they form a stable crystal lattice.

When doping occurs, the balance of valence electrons is disrupted. For example, sulfur (S), which has six valence electrons, when doped into indium antimonide (InSb), brings more electrons available to conduct current. Through an understanding of valence electrons in semiconductors, predicting the impact of specific impurities becomes simpler.

In the doping process, there are various mechanisms through which impurities can be incorporated into a semiconductor crystal. Substitutional impurities are one such type where foreign atoms replace the host atoms in the crystal lattice. This type of impurity is critical as it directly influences the semiconductors' electrical properties. For instance, arsenic (As) acting as a substitutional impurity in zinc telluride (ZnTe) would replace some of the tellurium atoms, contributing fewer valence electrons and creating holes.

Substitutional doping is responsible for the creation of both n-type and p-type materials, which are integral to semiconductors widely used in electronics. The precision of substitution is important because improper impurity placement can lead to defects that negatively affect the semiconductor's performance.