Deep-level defects and turn-on capacitance recovery characteristics in AlGaN/GaN heterostructures

Abstract

We report on turn-on capacitance recovery measurements as a simple shorttime method of evaluating carrier-trapping phenomena in a two-dimensional electron gas (2DEG) in the bulk region of AlGaN/GaN heterostructures, employing their Schottky barrier diodes. Using this technique, we have investigated an in-depth relation between deep-level defects and 2DEG carrier trapping in an AlGaN/GaN heterostructure with a GaN buffer layer containing a high C concentration. Steady-state photo-capacitance spectroscopy measurements revealed three C-related deep-level defects located at~2.07,~2.80 and 3.23 eV below the conduction band in the GaN buffer layer. Additionally, turn-on capacitance recovery measurements showed a large decrease in recovery time under white-light optical illuminations with long-pass filters between 370 and 390 nm. It is concluded that the~3.23 eV level is mainly responsible for the 2DEG carrier-trapping phenomena in the GaN buffer layer of the AlGaN/GaN heterostructure.

Electrical Investigation of Turn-On Capacitance Recovery Characteristics in Carbon-Doped AlGaN/GaN Hetero-Structures Grown on Si Substrates

“…The t on of the sample A is extremely short compared to that of conventional AlGaN/GaN hetero-structures with the same carbon concentration of 1 × 10 17 cm −3 grown on Al 2 O 3 substrates. 20 On the other hand, for the sample C with the high carbon concentration of 1 × 10 19 cm −3 , the capacitance cannot be recovered at all to the initial level even after the turn-on time of 300 s. The capacitance recovery reflects the restitution of the depletion layers electrically deformed by applying the off-bias stress voltages. This slow capacitance recovery observed definitely stems from deep-level defects in the GaN:C buffer layers.…”