Letter
Leakage current mechanisms of groove-type tungsten-anode GaN SBDs with ultra low turn-ON voltage and low reverse current

https://doi.org/10.1016/j.sse.2020.107807Get rights and content

Highlights

  • High-performance lateral GaN SBDs with low VON of 0.39 V and low IR of 1.6 × 10−9 A/mm.

  • In-depth analysis of the device leakage mechanism.

  • Three current transport mechanisms: TE, FPE and TAT.

Abstract

In this work, we report a high-performance lateral GaN Schottky barrier diode (SBD) with a low turn-on voltage (VON) of 0.39 V and low reverse current. Meanwhile we have proposed a model to comprehend the leakage current mechanism in this GaN SBDs. The reverse current transport mechanism was analyzed by temperature-dependent current–voltage (T-I-V) measurements. The results indicate that reverse current is dominated by thermionic emission (TE), Frenkel–Poole (FP) emission and trap assisted tunneling (TAT) near zero bias, at low and high reverse bias, respectively. The thermionic field emission (TFE) is found to be the main mechanism near the breakdown voltage (BV). The comparison shows Al2O3 passivation layer can effectively reduce leakage current.

Introduction

Due to its wide bandgap, high impact field strength, high electron mobility and saturation velocity of the two-dimensional electron gas (2DEG) at the hetero-junction interface [1], [2], GaN-based devices turn out to be competitive candidates for both DC and RF applications. Among those high performance GaN devices, AlGaN/GaN SBDs are widely studied for their low switching losses and high operation frequencies [3], [4], [5], [6], [7], [8].

In particular, groove-type SBDs [9], [10], [11], [12], [13], [14], [15], [38], [39] are capable of satisfying high current, low turn-on voltage (VON) and high breakdown voltage (BV) simultaneously. A high power FOM of 1.7 × 103 MW/cm2 with a low VON of 0.35 V can be achieved, making it an ideal rectifier for future high performance electronics [16].Through in-depth study of the reverse characteristics of these groove-type SBDs, we found that the soft breakdown has been exhibited in these devices as a result of a gradual increase in reverse leakage current compared to hard breakdown. In order to further increase the breakdown voltage, reduce the off-state loss of the device and get higher switching ratio, it’s necessary to understand the reverse leakage current mechanisms in this structure. Although there have been many discussions about leakage current of GaN-based devices, but they were applied to GaN-based high electron mobility transistors (HEMTs) [17], [18], [19], [20], metal insulator semiconductor high-electron mobility transistors (MIS-HEMTs) [21], or traditional planar-type lateral SBDs [22], [23], [24], [25], [26]. Due to its unique sidewall conduction channels, previous reports do not applicable to groove-type AlGaN/GaN SBD.

In this paper, we have carried out a comprehensive study on the current transport mechanism of groove-type SBDs on SiC substrate at various bias conditions by temperature-dependent current–voltage (T-I-V) measurements.

Section snippets

Experimental

In our experiment, the epitaxial layers were grown on a 500 μm SiC substrate by metal organic chemical vapor deposition (MOCVD), consisting of a 2 nm GaN cap layer, a 28 nm Al0.2Ga0.8N barrier layer, a 1 nm AlN spacer, a 1.3 μm GaN buffer layer, and a 50 nm AlN nucleation layer. Device structure and layer structure details are shown in Fig. 1. Device fabrication is started with mesa isolation by Cl2/BCl3 etching to a depth of 200 nm. Cathodes were formed subsequently by depositing Ti/Al/Ni/Au

Results and discussion

Fig. 2(a) shows the linear-scale and log-scale plot of the I-V curves at anode-cathode distances (LAC) = 4 μm with VON = 0.39 V extracted at the current density of 1 mA/mm. The breakdown characteristic of the fabricated groove-type Tungsten-anode GaN SBD is shown in Fig. 2(b) with BV of 321 V. The performance of our groove-type lateral GaN SBDs are benchmarked against some state-of-the-art groove-type lateral GaN SBDs and traditional planar-type lateral GaN SBDs in the plot of VON with versus

Conclusion

The I-V characteristics of the groove-type Tungsten-anode lateral GaN SBDs with various temperatures are analyzed as a function of different RA and Loverlap. The leakage current is determined by Loverlap formed at anode sidewalls and overlap. According to different T-I-V relationships, three possible conductive mechanisms are proposed. TE is considered to be dominated mechanism near zero bias at sidewalls, as shown in Fig. 7(a). With increasing reverse bias, FP emission gradually replace TE and

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

This work was supported by the National Key Science & Technology Special Project (Grant No. 2017ZX01001301).

Yanni Zhang received the B.S. degree from Xidian University, Xi'an, China, in 2017. She is currently pursuing the Ph.D. degree with the School of Microelectronics, Xidian University. Her research interest is wide bandgap semiconductor GaN and AlN based devices.

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    Yanni Zhang received the B.S. degree from Xidian University, Xi'an, China, in 2017. She is currently pursuing the Ph.D. degree with the School of Microelectronics, Xidian University. Her research interest is wide bandgap semiconductor GaN and AlN based devices.

    Jincheng Zhang received the M.S. and Ph.D. degrees from Xidian University, Xi’an, China, in 2001 and 2004, respectively. He is currently a Professor with Xidian University, Xi’an, China. His current interests include wide bandgap semiconductor GaN and diamond materials and devices. He has authored and coauthored more than 200 journal and conference papers.

    Hong Zhou received his Ph.D. degree at May 2017 from Purdue University. From June 2017 to Feb. 2018, he was a postdoc in University of California Berkely. He is now a professor in School of Microelectronics, Xidian University. His research focuses on fabrication, electrical and thermal measurement, and modeling of negative-capacitance Si FETs, wide bandgap GaN and ultra-wide bandgap β-Ga2O3 based FETs for both DC and RF applications. He has authored and coauthored more than 60 journal and conference papers.

    Tao Zhang received the B.Eng. degree from the Xidian University, Xi’an, China. He is currently pursuing the Ph.D. degree with the School of Microelectronics, Xidian University, Xi’an. His research interest is wide bandgap semiconductor GaN based lateral SBD for power switching application.

    Haiyong Wang received the B.Eng. degree from Guizhou University, Guizhou, China, where he is currently pursuing the Ph.D. degree with the School of Microelectronics.

    Zhaoqing Feng received the B.Eng. degree from Xidian University, Xi’an, China, where he is currently pursuing the Ph.D. degree with the School of Microelectronics.

    Yue Hao is currently a Professor of Microelectronics and Solid State Electronics with Xidian University, Xi’an, China. His current interests include wide bandgap materials and devices, advanced CMOS devices and technology, semiconductor device reliability physics and failure mechanism, and organic electronics. He has authored and coauthored more than 300 journal and conference papers. Prof. Hao is a member of the Chinese Academy of Sciences, China.

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