Yes, semiconductors can be doped with elements that do not have 3 or 5 valence electrons. Doping is the process of intentionally adding impurity atoms to a semiconductor material to alter its electrical properties. While the commonly used dopants for semiconductors like silicon and germanium often have 3 or 5 valence electrons, dopants with different valence electron counts can also be employed.
In fact, there are two main types of doping: n-type and p-type doping.
N-type doping: In n-type doping, impurity atoms are added to a semiconductor, creating extra electrons in the material. These dopants are often elements with 5 valence electrons like phosphorus (P) or arsenic (As). These extra electrons contribute to the semiconductor's conductivity.
P-type doping: In p-type doping, impurity atoms are added to a semiconductor, creating electron deficiencies or "holes" in the material. Dopants used for p-type doping often have 3 valence electrons, such as boron (B) or gallium (Ga). The absence of electrons in these positions allows for easier movement of "holes" and contributes to the semiconductor's conductivity.
So, while dopants with 3 or 5 valence electrons are commonly used, semiconductors can be doped with other elements depending on the desired properties and the specific application.