Resistivity of Various Materials

Classification by Resistivity

Materials are grouped into conductors, semiconductors, and insulators based on their resistivity values, arranged from lowest to highest.

• Conductors (e.g., metals): Resistivity in the range $10^{-8} \, \Omega \text{m}$ to $10^{-6} \, \Omega \text{m}$.
• Insulators (e.g., ceramic, rubber, plastics): Resistivity about $10^{18}$ times greater than metals (or more).
• Semiconductors (e.g., silicon, gallium arsenide): Resistivity lies between conductors and insulators, but with a special property — it decreases as temperature rises.

Key Physical Behaviour

• Good conductors follow Ohm’s law linearly over a wide range (dashed line in Figure 3.5). The solid line shows actual $V$ vs $I$ for a good conductor — still nearly linear.
• Semiconductors show a non-linear $V$–$I$ characteristic. For example, a diode (Figure 3.6) has very different scales for positive and negative voltages/currents.
• Gallium arsenide (GaAs) (Figure 3.7) shows a characteristic curve where current varies non-linearly with voltage — typical of many semiconductors.

Temperature Dependence of Resistivity in Semiconductors …