Material Constant
The equilibrium concentration of electrons and holes in an undoped semiconductor crystal determines the baseline electrical behavior of the substrate. At room temperature, intrinsic carrier density in silicon is approximately ten to the power of ten per cubic centimeter. This value represents the point where thermal excitation provides enough energy for electrons to jump across the bandgap.
Temperature Dependency
Exponential increases in the number of free carriers occur as the thermal energy of the lattice rises. This relationship makes intrinsic carrier density the primary driver of leakage currents in p-n junctions at elevated temperatures. High bandgap materials like gallium nitride maintain a much lower density than silicon.
Conductivity Limit
Pure semiconductors exhibit a minimum conductivity that is set by the carrier concentration. When doping levels are low the intrinsic carrier density dominates the electrical properties and renders the device uncontrollable.
Measurement Condition
Experimental determination of this parameter involves Hall effect measurements on high purity crystals under controlled thermal environments. Accurate values for intrinsic carrier density are necessary for calibrating physics based device models used in semiconductor manufacturing. Variations in the crystal lattice structure or the presence of trace impurities shift the measured density away from theoretical predictions.
