化合物半導體加工中的表徵（簡體書）

Resistivity and carrier concentration and mobility are easily obtained by Hall effectmeasurements. Temperature-dependent Hall measurements provide carrier compensation ratio, total impurity density, ionization energy, and dominant scatteringmechanism. Extending the technique to high variable magnetic fields (-12 T) allowsmagnetoresistance characterization of mobile carriers in two-dimensional conducting channels and of quantized state energies.
Samples require a well-defined conducting-layer thickness or conducting channel.
Isolation of the channel from the substrate can be achieved by ion implantation orepitaxial growth. No isolation is required if bulk material (e.g., substrates or thickslabs) is to be characterized. Ohmic contacts are placed onto patterns such as a squareslab, Van der Pauw (VDP or clover-leaf) pattern, or Hall bar. The square slab is theeasiest, the VDP has the best contact placement error immunity, and the Hall bar isthe most appropriate for magnetoresistance measurements. Sample dimensions areon the order of 1 cm.
The Hall effect technique uses a four point probe geometry and exploits theLorentz force behavior of mobile carriers in an applied magnetic field to extract the"Hall coefficient," RH, which is directly related to the carrier density. By combiningconcurrent resistivity measurements on the same sample, extraction of free carrierconcentration, type, and mobility are possible. In the simplest method, a constantcurrent is applied between two contacts and the voltage is measured across the othertwo. Application of a magnetic field (-2 kG) creates a charge density imbalance thatproduces a voltage across the two contacts located perpendicular to the current flowdirection. The magnitude of the voltage is directly proportional to the mobility； thepolarity indicates the carrier type.