NettoTrägerkonzentration

NettoTrägerkonzentration is a term used in semiconductor physics to describe the net density of mobile charge carriers in a material, typically electrons and holes. The densities of electrons and holes are denoted by n and p, respectively. The net carrier concentration is often written as Δn = n − p. Its sign determines the majority carrier type: Δn > 0 indicates electron-dominated (n-type) conduction, while Δn < 0 indicates hole-dominated (p-type) conduction. In intrinsic (undoped) silicon or germanium, n and p are equal, so Δn = 0.

Two related concepts are important. First, the intrinsic relation n p = n_i^2, where n_i is the intrinsic carrier concentration, governs how n and p respond to temperature and generation-recombination processes. Second, doping introduces fixed charges via donors (N_D) and acceptors (N_A). The net dopant concentration N_D − N_A (often written as N_D − N_A or ΔN) determines the majority carrier type and, under common approximations, sets the order of magnitude of the free carrier density: for n-type materials with N_D > N_A, n ≈ N_D − N_A and p ≪ n; for p-type materials with N_A > N_D, p ≈ N_A − N_D and n ≪ p. In more accurate treatments, charge neutrality and generation-recombination adjust both n and p while respecting n p = n_i^2.

The NettoTrägerkonzentration is central to predicting electrical properties such as conductivity, given by σ = q (μ_n n + μ_p p), where μ_n and μ_p are electron and hole mobilities. It also influences device behavior in diodes and transistors, where changes in Δn alter current flow, depletion regions, and the Fermi level.

In summary, NettoTrägerkonzentration captures the net mobile carrier content and its sign, linking material composition, temperature, and electrical performance.