Nicolo Ronchi
Katholieke Universiteit Leuven
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Featured researches published by Nicolo Ronchi.
IEEE Transactions on Electron Devices | 2013
Marleen Van Hove; Xuanwu Kang; Steve Stoffels; D. Wellekens; Nicolo Ronchi; Rafael Venegas; Karen Geens; Stefaan Decoutere
Au-free GaN-based metal-insulator-semiconductor high electron-mobility transistors grown on 150-mm Si substrates are reported. The device characteristics for three different processes are compared: an ohmic-first and a gate-first process with Al<sub>2</sub>O<sub>3</sub>-only as gate dielectric and a novel approach with a bilayer gate dielectric stack consisting of Si<sub>3</sub>N<sub>4</sub> and Al<sub>2</sub>O<sub>3</sub>. The Si<sub>3</sub>N<sub>4</sub> layer was deposited in situ in the metal-organic chemical vapor deposition reactor in the same growth sequence as the rest of the epilayer stack and the Al<sub>2</sub>O<sub>3</sub> layer was deposited ex situ by atomic layer deposition. Only the process with the bilayer gate dielectric results in robust devices with a breakdown voltage >600 V. The ohmic contact resistance for Au-free Ti/Al/W metallization scheme is <;1 Ω·mm. The devices show high maximum output current density (>0.4 A/mm); and low gate and drain leakage (<;10<sup>-10</sup> A/mm). The maximum pulsed mode drain-source current of power bars with 20 mm gate width is 8 A. The specific on-state resistance is 2.9 m Ω·cm<sup>2</sup>.
IEEE Transactions on Electron Devices | 2016
Jie Hu; Steve Stoffels; Silvia Lenci; Benoit Bakeroot; Brice De Jaeger; Marleen Van Hove; Nicolo Ronchi; Rafael Venegas; Hu Liang; Ming Zhao; Guido Groeseneken; Stefaan Decoutere
In this paper, a further leakage reduction of AlGaN/GaN Schottky barrier diodes with gated edge termination (GET-SBDs) has been achieved by optimizing the physical vapor deposited TiN as the anode metal without severe degradation of ON-state characteristics. The optimized GET-SBD multifinger power diodes with 10 mm anode width deliver ~4 A at 2 V and show a median leakage of 1.3 μA at 25 °C and 3.8 μA at 150 °C measured at a reverse voltage of -200 V. The temperature-dependent leakage of Si, SiC, and our GaN power diodes has been compared. The breakdown voltage (BV) of GET-SBDs was evaluated by the variation of anode-to-cathode spacing (LAC) and the length of field plate. We observed a saturated BV of ~600 V for the GET-SBDs with LAC larger than 5 μm. The GET-SBD breakdown mechanism is shown to be determined by the parasitic vertical leakage current through the 2.8 μm-thick buffer layers measured with a grounding substrate. Furthermore, we show that the forward voltage of GET-SBDs can be improved by shrinking the lateral dimension of the edge termination due to reduced series resistance. The leakage current shows no dependence on the layout dimension LG (from 2 to 0.75 μm) and remains at a value of ~10 nA/mm. The optimized Au-free GET-SBD with low leakage current and improved forward voltage competes with high-performance lateral AlGaN/GaN SBDs reported in the literature.
Microelectronics Reliability | 2014
Jie Hu; Steve Stoffels; Silvia Lenci; Nicolo Ronchi; Rafael Venegas; Shuzhen You; Benoit Bakeroot; Guido Groeseneken; Stefaan Decoutere
Dynamic characterization (Pulsed I–V) on Au-free AlGaN/GaN Schottky Barrier Diodes (SBDs) has been performed to evaluate the impact of negative quiescent biases on the forward characteristics. Results show an increase of on-resistance when more negative quiescent biases are applied, and a sudden current collapse phenomenon when the quiescent bias exceeds 175 V. Furthermore, the measurements show a common signature: the total current collapse is the result of the trapping phenomena occurring around the Schottky contact corner. The trap levels of 0.5 eV and 1.0 eV have been characterized from current transient spectroscopy. A TCAD model with these two trap levels as donor states at the Si3N4/AlGaN interface has been defined, to understand their role and explain the observed behavior of AlGaN/GaN SBDs from this dynamic measurement. We propose that trapping at deep energy levels (Trap1 = 1.0 eV), existing at the Si3N4/AlGaN interface, is responsible for the gradual current reduction observed for negative quiescent biases up to Anode-to-Cathode voltage (VAC )o f175 V. The electron filling at the shallower traps with high density at energy level located 0.5 eV starts at higher reverse biases, resulting in a strong Fermi-level pinning, which can be the cause of sudden current collapse. 2014 Published by Elsevier Ltd.
IEEE Transactions on Electron Devices | 2016
Jie Hu; Steve Stoffels; Silvia Lenci; Brice De Jaeger; Nicolo Ronchi; Andrea Natale Tallarico; D. Wellekens; Shuzhen You; Benoit Bakeroot; Guido Groeseneken; Stefaan Decoutere
In this paper, we have extensively investigated the impact of anode recess on the reverse leakage current, forward voltage (VF), and dynamic characteristics of Au-free AlGaN/GaN Schottky barrier diodes with a gated edge termination (GET-SBDs) on 200-mm silicon substrates. By increasing the number of atomic layer etching (ALE) cycles for anode recessing, we have found that: 1) the reverse leakage current is strongly suppressed due to a better electrostatic control for pinching off the channel in the GET region; a median leakage current of ~1 nA/mm and an ION/IOFF ratio higher than 108 have been achieved in GET-SBDs with six ALE cycles; 2) the forward voltage (~1.3 V) is almost independent of the ALE cycles, taking into account its statistical distribution across the wafers; 3) when the remaining AlGaN barrier starts to be very thin (in the case of six ALE cycles), a spread of the ON-resistance, mainly attributed to the GET region, can occur due to the difficult control of the remaining AlGaN thickness and surface quality; and 4) the dynamic forward voltage of GET-SBDs shows a mild dependence on the ALE process in pulsed I-V characterization, and a more ALE-dependent dynamic ON-resistance is observed.
international symposium on power semiconductor devices and ic s | 2016
Niels Posthuma; Shuzhen You; Hu Liang; Nicolo Ronchi; Xuanwu Kang; D. Wellekens; Y. N. Saripalli; Stefaan Decoutere
The p-GaN gate HEMT device architecture is a prime contender for normally-off GaN power transistors. In this work the growth parameters of the Mg doped p-type GaN layer are varied and the impact of Mg out-diffusion and Mg activation on the main HEMT device parameters is studied. The Mg chemical concentration is optimized together with the Mg active concentration to obtain improved device performance. Enhancement mode 36 mm p-GaN gate power transistors have been realized, featuring a threshold voltage of 2.1 V and a Ron of 150 ma.
international symposium on power semiconductor devices and ic's | 2014
Silvia Lenci; Jie Hu; Marleen Van Hove; Nicolo Ronchi; Stefaan Decoutere
In this work we show the impact of surface cleaning on the dynamic characteristics of Au-free AlGaN/GaN Gated Edge Termination Schottky Barrier Diodes (GET-SBDs). It is demonstrated that the current dispersion (measured in pulsed regime) can be reduced by introducing a N2 plasma cleaning step in the anode metal deposition chamber. Moreover, diodes treated with N2 plasma show lower current drop after reverse voltage stress (with a relative forward voltage increase of 2% after stress) than diodes without clean or with Atomic Layer Etching (ALE) clean (20% and 37% relative forward voltage increase, respectively).
european solid state device research conference | 2014
Fabio Alessio Marino; Davide Bisi; Matteo Meneghini; G. Verzellesi; Enrico Zanoni; Marleen Van Hove; Shuzhen You; Stefaan Decoutere; Denis Marcon; Steve Stoffels; Nicolo Ronchi; Gaudenzio Meneghesso
Breakdown mechanisms in AlGaN/GaN HEMT devices are here analyzed, placing particular emphasis in the analysis of GaN based device grown on silicon substrate. Based on combined experimental data and bi-dimensional numerical simulation we demonstrate that many physical mechanisms can contribute to increase the leakage current leading to the final breakdown of the device. In particular we show how band-to-band phenomena, rather than impact ionization, can be responsible of the premature breakdown even in double-heterostructure HEMTs.
Japanese Journal of Applied Physics | 2015
Jie Hu; Steve Stoffels; Silvia Lenci; Tian-Li Wu; Nicolo Ronchi; Shuzhen You; Benoit Bakeroot; Guido Groeseneken; Stefaan Decoutere
In this work, we perform an in-depth analysis of electron-trapping in AlGaN/GaN Schottky barrier diodes under constant voltage (VAC = %100V) off-state stress conditions. The current–voltage (I–V) characteristics of the diode after stressing show a leakage reduction and on-state degradation due to electron-trapping occurring in the vicinity of the Schottky contact. Capacitance–voltage (C–V) measurements confirm an increase of the barrier height and the on-resistance of the stressed device. Furthermore, the on-resistance increase has been studied with different temperatures and stressing times. By TCAD simulations, a lateral extension of the “trapped region” at the AlGaN/Si3N4 interface has been visualized and can qualitatively explain the phenomenon of higher on-resistance increase at higher temperatures.
Japanese Journal of Applied Physics | 2015
Nicolo Ronchi; Brice De Jaeger; Marleen Van Hove; Robin Roelofs; Tian-Li Wu; Jie Hu; Xuanwu Kang; Stefaan Decoutere
In this work we will present the experimental path followed to optimize the dynamic ON-resistance (RDS-ON) dispersion and to reduce the threshold voltage shift of AlGaN/GaN transistors grown on 200 mm Si wafers. Firstly, it will be demonstrated that a SiN gate dielectric grown by means of plasma enhanced atomic layer deposition (PEALD) instead of rapid thermal chemical vapor deposition (RTCVD) reduces threshold voltage (Vth) shift induced by negative gate bias and the gate leakage. Secondly, the dynamic RDS-ON dispersion of two wafers with same gate dielectric (PEALD SiN) but different in situ metal organic chemical vapor deposition (MOCVD) capping layer, GaN or SiN, is compared. Results will show that the traps at the surface causing the RDS-ON dispersion can drastically be reduced by using in situ MOCVD SiN.
international symposium on power semiconductor devices and ic s | 2016
Silvia Lenci; Jie Hu; Nicolo Ronchi; Stefaan Decoutere
This work reports on Au-free AlGaN/GaN lateral Schottky diodes on 200 mm Si substrate, with both optimized DC and dynamic characteristics and anode width ranging from 100 μm until 100 mm. 100 mm-wide diodes show low leakage (within 1 μA/mm at anode-cathode voltage Vac = -200V) and low on-state voltage (i.e., Vac at 100 mA/mm forward current) within 1.35 V. Reduced current collapse is achieved by in-situ N2 plasma clean in combination with an in-situ SI3N4 capping layer.