Trap state analysis in AlGaN/GaN/AlGaN double heterostructure high electron mobility transistors at high temperatures

Abstract

In this work, frequency-dependent capacitances and conductance measurements are adopted to investigate high temperature characteristics of trap states in AlGaN/GaN/AlGaN double heterostructure high electron mobility transistors (DH-HEMTs). It is found that fast and slow trap states are present in DH-HEMTs, while only fast traps exist in AlGaN/GaN single heterostructure (SH) HEMTs. In the former, the fast trap state density ranges from 4.6 × 1012 cm−2 eV−1 to 1.9 × 1013 cm−2 eV−1 located at an energy below the conduction band between 0.273 eV and 0.277 eV, and the slow deep trap state density decreases from 2.4 × 1013 cm−2 eV−1 to 8.7 × 1012 cm−2 eV−1 located at an energy ranging from 0.384 eV to 0.423 eV in DH-HEMTs with a 14 nm GaN channel layer. These active trap energy levels in DH-HEMTs become deeper as the thickness of the channel layer decreases. In addition, the active trap energy levels in SH- and DH-HEMTs gradually become deeper as the measurement temperature increases. Also, the change in amplitude of the active trap energy levels in DH-HEMTs is larger than that in SH-HEMTs, which indicates that DH is efficient in suppressing the reverse gate leakage current at high temperatures.