Doping and other materials parameters influence the properties of III–V devices in a profound manner. Examples of device parameters which are strongly influenced by the defect and doping concentration are the radiative efficiency of a laser, the minority carrier lifetime in the base of a bipolar transistor, the carrier mobility in the channel of a field-effect transistor, or the quantum efficiency of a pin photo-diode. In this chapter, characterization techniques are discussed that relate directly to shallow impurities as well as deep centers. The characterization techniques are categorized as (i) electronic (ii) optical, and (iii) chemical and structural techniques. Fundamental aspects of characterization techniques as well as practical ‘hints’ for the experimentalist are emphasized.

Electronic characterization techniques

Many properties of semiconductors that relate directly to impurities or defects can be assessed by electrical measurements. Such measurements include current–voltage, capacitance–voltage, resistivity, magnetoresistance, and impedance measurements. Frequently, temporal transients of such measurements are of interest, for example the capacitance transient after a semiconductor has been subjected to an electrical pulse. In this section, the Hall effect, capacitance–voltage (CV) profiling technique, deep level transient spectroscopy (DLTS), thermally stimulated capacitance (TSCAP), thermally stimulated current (TSC), and admittance spectroscopy are discussed.

Hall effect measurements

Hall effect measurements (Hall, 1879) allow one to determine the (majority) Hall carrier concentration of unipolar semiconductors in which the minority carrier concentration can be neglected.