Current transient spectroscopy for trapping analysis on Au-free AlGaN/GaN Schottky barrier diode

Abstract

This paper presents a combined technique of high voltage off-state stress and current transient measurements to investigate the trapping/de-trapping characteristics of Au-free AlGaN/GaN Schottky barrier diodes. The device features a symmetric three-terminal structure with a central anode contact surrounded by two separate cathodes. Under the diode off-state stress conditions, the two separate cathodes were electrically shorted. The de-trapping dynamics was studied by monitoring the recovery of the two-dimensional electron gas (2DEG) current at different temperatures by applying 0.5 V at cathode 2 while grounding cathode 1. During the recovery, the anode contact acts as a sensor of changes in diode leakage current. This leakage variation was found to be mainly due to the barrier height variation. With this method, the energy level and capture cross section of different traps in the AlGaN/GaN Schottky barrier diode can be extracted. Furthermore, the physical location of different trapping phenomena is indicated by studying the variation of the diode leakage current during the recovery. We have identified two distinct trapping mechanisms: (i) electron trapping at the AlGaN surface in the vicinity of the Schottky contact which results in the leakage reduction (barrier height ϕB increase) together with RON degradation; (ii) the electron trapping in the GaN channel layer which partially depletes the 2DEG. The physical origin of the two different traps is discussed in the text.

Stability and Reliability of Lateral GaN Power Field-Effect Transistors

“…For medium times (∼10s of s at RT), I D recovers but I G drops with time [25]. For longer times (∼1000s of s), both I D and I G recover in sync [25].…”

“…Detrapping transients of I G and I D provide further insights [25]. These are also generally slow, in the few second range at RT, with very well-defined time constants that are thermally activated [20], [25].…”

“…These are also generally slow, in the few second range at RT, with very well-defined time constants that are thermally activated [20], [25]. For medium times (∼10s of s at RT), I D recovers but I G drops with time [25]. For longer times (∼1000s of s), both I D and I G recover in sync [25].…”

“…I Dlin and I Dsat also drop and R ON increases. Terms such as current collapse or dynamic R ON are often used to describe this [20], [23]- [25]. Simultaneously to the onset of these phenomena, an increase in the gate Schottky barrier height has been observed [25].…”

“…Terms such as current collapse or dynamic R ON are often used to describe this [20], [23]- [25]. Simultaneously to the onset of these phenomena, an increase in the gate Schottky barrier height has been observed [25]. Very slow trapping transients, in the few second range at room temperature (RT), are generally observed.…”