Gap state transport in annealed low temperature grown GaAs inferred from the properties of Al/LT GaAs/n+GaAs Schottky diodes

We have probed transport mechanisms in Al/low temperature (LT) grown GaAs/n⁺GaAs Schottky diodes through their I-V characteristics as a function of temperature and through their AC conductivity at room temperature. The structures show features of rectification and series resistance. The former is analysed in terms of thermionic emission-tunneling theory and shows the temperature dependent ideality factor close to three, characteristic of tunneling through the depletion barrier of the n⁺ substrate. Electrons are injected through this barrier into gap states in the LT GaAs layer. The series resistance versus temperature shows an Arrhenius type behaviour with an activation energy of 32 meV, while the frequency-dependent AC conductivity behaves as ω^s with s=0.65. These observations are consistent with hopping through gap states