A SIMPLE AND RELIABLE METHOD OF THERMOELECTRIC EFFECT SPECTROSCOPY FOR SEMIINSULATING III-V SEMICONDUCTORS

We have developed a simpler and more reliable method of thermoelectric effect spectroscopy (TEES), eliminating the second heater in the technique. We have applied this method to the deep level studies in the semi-insulating undoped or Cr-doped GaAs materials and in the GaAs epitaxial layers grown at a low temperature by molecular beam epitaxy. We have found that the electrical contacts made on front and back surfaces of the sample are more reliable for the TEES measurement than both contacts made on the same surface. In this contact arrangement, the temperature difference of about 1-2 K between the back and front surfaces is enough to produce a clear and reliable TEES data, without the need for a second heater. The results obtained by TEES are consistent with the results obtained by photoinduced transient spectroscopy (PITS) and by thermally stimulated current (TSC) measurements. The TEES results clearly distinguish between the electron traps and the hole traps. We discuss the results on the various semi-insulating GaAs samples and the advantages and limitations of the TEES technique.