PHOTOTHERMOELECTRIC AND THERMALLY STIMULATED THERMOELECTRIC EFFECTS - TECHNIQUES IN PHOTOELECTRONIC ANALYSIS

Thermoelectric power measurements have seldom been used to investigate the photoelectronic properties of semiconductor crystals. This paper presents the results of an exploratory investigation of thermoelectric power in three different specific situations: (1) the effect on thermoelectric power of extrinsic photoexcitation involving imperfection states in the crystal, (2) the effect on thermoelectric power of optical quenching of photoconductivity, and (3) thermally stimulated thermoelectric power, associated with the emptying of electron and hole traps in the crystal. The increased sensitivity of the thermoelectric effect to two-carrier phenomena as compared to the Hall effect, makes it a valuable effect for investigating the contribution of electrons and holes to photoelectronic behavior. The results obtained with single-crystal CdS suggest that: (1) The thermoelectric effect is quite useful in imperfection-level spectroscopy, (2) Sensitizing imperfections for photoconductivity have a complex dipole-like structure, and (3) Holes play a larger role in photo-electronic effects than commonly attributed. Further investigations of the techniques using thermoelectric power are certainly indicated. © 1968 The American Institute of Physics.