Modified space-charge-limited current behavior in pulsed laser deposited (Ba,Sr)TiO3 thin films

(Ba,Sr)TiO3 film was epitaxially grown on a cleaved single crystal 100 MgO substrate by pulsed laser deposition (PLD). Less exponential values m (m < 2) were observed in current-voltage (I-V) characteristics measured at different temperatures in the space-charge-limited (SCL) region. m is defined by current-voltage relationship: I ∝ Vm. This behavior was explained with a developed space-charge-limited current (SCLC) model based on field-dependent dielectric constant. Considering field-dependent constant, there must be a shallow energy level near the conduction band according to I-V characteristics. The distribution of this level is exponential with a characteristic temperature Tt = 1141 K. The total density of states is Nt = 4 × 1016 cm−3 determined by charge-based deep-level transient spectra (Q-DLTS). We suppose this level is introduced by oxygen vacancies. The temperature-dependent I-V characteristics account for the capturing and detrapping electrons from this level with activation energy Ea = 0.309 eV.