Transport mechanisms of leakage current in Al2O3/InAlAs MOS capacitors

• The transport mechanisms of leakage current in Al2O3/InAlAs MOS capacitors at different temperatures are investigated.
• The leakage current at positive bias is found to be dominated by Schottky emission.
• The leakage current at negative bias is found to be dominated by Frenkel–Poole emission.
• The reason of different dominating transport mechanisms at positive and negative biases is explained.

An Al2O3 layer is inserted between the InAlAs layer and the metal gate in InAs/AlSb HEMTs to suppress the leakage current. The transport mechanisms of leakage current in Al2O3/InAlAs metal–oxide–semiconductor (MOS) capacitors at both positive and negative biases at different temperatures ranging from 10 °C to 70 °C are investigated. For positive bias, the leakage current is dominated by Schottky emission. Based on the fitted straight lines, the relative dielectric constant of Al2O3 and the barrier height between Al2O3 and InAlAs are extracted. However, for negative bias, the leakage current is dominated by Frenkel–Poole (F–P) emission and the depth of the trap energy level from the conduction band (ϕtϕt) is extracted. Furthermore, authors explain the reason why the dominating mechanisms at positive and negative biases are different.