[paper] Effect of the AC-Signal Frequency on Flat-Band Voltage of Al/HfO2/SiO2/Si Structures

Andrzej Mazurak, Bogdan Majkusiak

Investigation of the Anomalous Effect of the AC-Signal Frequency 

on Flat-Band Voltage of Al/HfO2/SiO2/Si Structures

Solid-State Electronics (2021) SSE 108107 

DOI:10.1016/j.sse.2021.108107

*TU Warsaw, Institute of Microelectronics and Optoelectronics, Koszykowa 75, 00-662 Warsaw, Poland

Abstract: MIS structures with double-layer HfO2/SiO2 gate stacks were fabricated. The admittance measurements revealed an anomalous voltage shift of the capacitance-voltage characteristics, modulated by the ac signal frequency. The effect is discussed in terms of the oxide charge modulation through the frequency dependent leakage mechanism.

Fig: Measured Gpm conductance–voltage characteristics for the n-type MIS structure.

• An anomalous effect of the ac-signal frequency on the voltage shift of the CV characteristics of Al/HfO2/SiO2/Si devices was observed.
• The observed effect is stable, reproducible, and reversible and is not driven by the measurement procedure or the measurement protocol parameters.
• The effect is explained through a frequency dependent leakage conductance which affects the electric charge trapped interior the gate stack.
• A linear dependence of the leakage conductance on the ac signal frequency is observed.

[paper] Fabrication EM AlGaN/GaN MIS HEMT

Flavien Cozette¹, Bilal Hassan¹, Christophe Rodriguez¹, Eric Frayssinet², Rémi Comyn², François Lecourt³, Nicolas Defrance⁴, Nathalie Labat⁵, François Boone¹, Ali Soltani¹, Abdelatif Jaouad¹, Yvon Cordier² and Hassan Maher¹

New barrier layer design for the fabrication of gallium nitride-metal-insulator-semiconductor-high electron mobility transistor normally-off transistor

2021 Semicond. Sci. Technol. 36 034002

DOI: 10.1088/1361-6641/abd489

¹LN2, CNRS-UMI-3463, 3IT, Université de Sherbrooke, Canada

²Université Côte d'Azur, CNRS, CRHEA, Valbonne, France

³OMMIC, 94450 Limeil-Brévannes, France

⁴IEMN, CNRS-UMR-8520, University of Lille, France

⁵IMS, CNRS-UMR-5218, University of Bordeaux, France

Abstract: This paper reports on the fabrication of an enhancement-mode AlGaN/GaN metal-insulator-semiconductor-high electron mobility transistor with a new barrier epi-layer design based on double Al0.2Ga0.8N barrier layers separated by a thin GaN layer. Normally-off transistors are achieved with good performances by using digital etching (DE) process for the gate recess. The gate insulator is deposited using two technics: plasma enhance chemical vapour deposition (sample A) and atomic layer deposition (sample B). Indeed, the two devices present a threshold voltage (Vth) of +0.4 V and +0.9 V respectively with ΔVth about 0.1 V and 0.05 V extracted from the hysteresis gate capacitance measurement, a gate leakage current below 2 × 10−10 A mm−1, an ION/IOFF about 108 and a breakdown voltage of VBR = 150 V and 200 V respectively with 1.5 µm thick buffer layer. All these results are indicating a good barrier surface quality after the gate recess. The DE mechanism is based on chemical dissolution of oxides formed during the first step of DE. Consequently, the process is relatively soft with very low induced physical damages at the barrier layer surface.

Fig: SEM image of an E-mode device.

Acknowledgments: This work was supported by Fonds de Recherches du Québec—Nature, Technologies (FRQNT), the Natural Sciences and Engineering Research Council of Canada (NSERC), French technology facility network RENATECH and the French National Research Agency (ANR) through the projects ED-GaN (ANR-16-CE24-0026-02) and the 'Investissements d'Avenir' program GaNeX (ANR-11-LABX-0014).