Physical origin of current collapse in Au-free AlGaN/GaN Schottky Barrier Diodes

Physica Status Solidi (a)

Lenci

et al. 2016

We investigate the DC and dynamic characteristics of AlGaN/GaN Schottky barrier diodes (SBDs) and the diodes with a gated edge termination (GET‐SBD) fabricated on unintentional doped (UID) and carbon‐doped AlGaN buffers. The off‐state characteristics of diodes fabricated on UID buffer are dominated by buffer leakage and buffer breakdown voltage (BV) at higher reverse voltage (VR larger than 300 V). An improvement in diode leakage and BV can be obtained by fabricating the GET‐SBDs on C‐doped buffers. A pronounced RON degradation of the AlGaN/GaN SBDs and GET‐SBDs on carbon‐doped buffers was observed by dynamic pulsed I−V characterization. This dynamic RON degradation causes a clear forward current reduction for the AlGaN/GaN GET‐SBDs. From combined off‐state stress and current transient measurements on AlGaN/GaN SBDs, the collapsed current is recoverable and the RON degradation is due to a temporary trapping mechanism occurring in the buffer. A distinct trap level of 0.57 eV from trap spectra has been extracted for the diode fabricated on C‐doped buffer, and the value was implemented in a TCAD simulator. The simulated results confirm a bulk trapping in the buffer layer for the SBD and show an additional trapping region in the GET‐SBD architecture.

Section: Resultsmentioning

confidence: 99%

“…To evaluate the dynamic characteristics and trapping effects in AlGaN/GaN SBDs, pulsed

I - V

and current transient spectroscopy were done with the Agilent B1505A. Pulsed forward

I - V

characteristics are measured with a 10‐ms stress pulse (quiescent state) preceding each

I - V

point (). The stressing pulse at a negative voltage (

V_{R}

) is changed from 0 V to

- 100

V to evaluate the bias‐dependent trapping mechanisms.…”

Section: Experimental Methodologymentioning

confidence: 99%

Leakage and trapping characteristics in Au‐free AlGaN/GaN Schottky barrier diodes fabricated on C‐doped buffer layers

Physica Status Solidi (a)

Lenci

et al. 2016

“…Finally, Hu et al [23] by combining experimental and simulation results have proposed the physical origin of the current collapse and ON-resistance degradation in Au-free AlGaN/GaN SBDs occurring when a negative bias is applied on the anode. In particular, they have linked the gradual increase in the R ON to those traps featuring an energy of 1 eV below the conduction band and located at Si 3 N 4 /AlGaN interface.…”

Section: Introductionmentioning

confidence: 99%

Reliability of Au-Free AlGaN/GaN-on-Silicon Schottky Barrier Diodes Under ON-State Stress

Tallarico

IEEE Trans. Electron Devices

Magnone

et al. 2016

In this paper, we report the results of an experimental analysis of the degradation induced by ON-state stress in GaN-based Schottky barrier diodes (SBDs). When a high stress current is applied to the device, turn-ON voltage (V TON ), forward voltage (V F ), and ON-resistance (R ON ) are affected by charge carrier trapping occurring at the AlGaN surface close to the anode corners and/or into the AlGaN barrier layer. We have investigated the degradation of SBDs under different stress conditions, analyzing the influence of temperature and voltage, investigating the activation energy of the traps, and hence the trapping mechanisms. In addition, thanks to this approach, the device lifetime has been evaluated, proving good device reliability.

“…During the off-state operation, the SBD is subjected to a high electric field condition, which gives rise to electron injection and trapping phenomena at the AlGaN surface (at the corner of the Schottky contact) or in the GaN channel and AlGaN buffer layers. 17 As shown in Fig. 1(b), the conduction band will be lifted up due to the trapped electrons (in the AlGaN barrier and in the GaN channel layer) resulting in a lower 2DEG density compared with the fresh condition.…”

mentioning

confidence: 98%

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

Applied Physics Letters

Lenci

et al. 2015

Self Cite

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.