Trap states in enhancement-mode double heterostructures AlGaN/GaN high electron mobility transistors with different GaN channel layer thicknesses

Abstract

This is the report on trap states in enhancement-mode AlGaN/GaN/AlGaN double heterostructures high electron mobility transistors by fluorine plasma treatment with different GaN channel layer thicknesses. Compared with the thick GaN channel layer sample, the thin one has smaller 2DEG concentration, lower electron mobility, lower saturation current, and lower peak transconductance, but it has a higher threshold voltage of 1.2 V. Deep level transient spectroscopy measurements are used to obtain the accurate capture cross section of trap states. By frequency dependent capacitance and conductance measurements, the trap state density of (1.98–2.56) × 1012 cm−2 eV−1 is located at ET in a range of (0.37–0.44) eV in the thin sample, while the trap state density of (2.3–2.92) × 1012 cm−2 eV−1 is located at ET in a range of (0.33–0.38) eV in the thick one. It indicates that the trap states in the thin sample are deeper than those in the thick one.