engleski

Thermoelectric Effect Spectroscopy Measurements on Semi-Insulating GaN

A new, simplified set-up for the thermoelectric effect spectroscopy (TEES) particularly suitable for film-on-substrate sample type, was devised. The temperature gradient along the sample was achieved without additional heater. Set-up was then applied for measurements on the semi-insulating GaN, grown at sapphire substrate in order to investigate deep level?s (trap?s) sign. TEES currents were found negative at lower temperatures and positive at higher temperatures, indicating that shallower levels belong to electron traps, and deeper levels to hole traps. Deep traps were further characterized by using the thermally stimulated current (TSC) measurements and the simultaneous multiple peak analysis (SIMPA) method. The shallowest observed electron and hole traps had activation energies Ec-0.09 eV and Ev+0.167 eV, respectively. It is argued that these defects are related to N-vacancy and Ga-vacancy, respectively. Both trap types were found in relatively high concentrations causing the electrical compensation and high resistivity.

deep levels; thermoelectric effect spectroscopy; TSC; GaN

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