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Noëlle Gogneau
Tel: (+33) 1 69 63 61 75
Groupe: Elaboration et Physique des Structures Epitaxiées
Actions: Nanowires , QD

From Single III-Nitride Nanowires to III-N NW-based Piezo-Generators :
Towards Wireless micro-devices

Pss-Cover.png Select Paper.png

The nomad electronic devices are today ubiquitous in our daily life and the question of their energetic autonomy has become a key challenge. From now few years, 1D-nanostructures, such as nanowires, have emerged as a promising solution to efficiently harvest the vibrational and deformation energies found in the environment and convert them into useful electrical energy without any external energy source requirement. From now few years, III-nitride Nanowires have started to be explored for developing piezo-generator devices thanks to their high piezoelectric coefficients and their strong piezo-generation response.

We aim to develop ultra-compact and high-efficient piezo-generators integrating vertical array of III-Nitride NWs for powering micro-devices, such as sensors, medical implants or nomad electronics. Our approach is based on a systematic multi-scale analysis, going from single wire properties to macroscopic device fabrication and characterization, which allows to establish for GaN NWs the relationship between the material properties and the piezo-generation and to propose an efficient piezo-generator design.

To avoid confusion :

The concept of Nanogenerator defines the ability of a single NW to convert a mechanical deformation into useful electrical energy. Nanogenerator concept2.png
Piezo-generator concept2.png The concept of Piezo-generator defines a macroscopic device integrating an array of 1D nanostructures (i.e. an array of nanogenerators) and generating piezoelectric energy in response to its deformation.

GaN NWs :

GaN NWs.png Self-assembled GaN NWs are grown by Plasma-Assisted Molecular Beam Epitaxy on Si(111) substrate. Prior to the growth of GaN NWs, a 2.5 nm-thick AlN buffer layer was deposited. This AlN underlayer allows a better control of the NW nucleation, density and orientation and prevents the formation of the insulating SiN layer between the GaN NWs and the Si(111) substrate, which annihilates the piezoelectric generation.
Our GaN NWs are vertically aligned with hexagonal shape delimited by {10-10} planes and they are characterized by a N-polar surface (N-polarity).

Piezoelectric properties of III-N NWs :

We investigate the piezoelectric properties of single GaN NWs by atomic force microscope (AFM) in vertical configuration equipped with a modified Resiscope module allowing real-time electrical measurements (GEEPs Lab). We have demonstrated the high potential of n-type and p-type GaN NWs to convert a mechanical deformation into an electrical energy. We have demonstrated the best mechanical-electrical conversion from GaN NWs in terms of the output voltage, with a maximum generated voltage of about 440 mV per nanowire.
GaN nanowires for piezoelectric generators Phys. Status Solidi RRL 2014 Pss-Cover.png

Mechanical-electrical conversion mechanisms in III-N NWs :

We demonstrate the strong relationship between the structural and electrical (doping) properties of the GaN NWs and the establishment of the piezo-electric potential inside the nanostructures when they are submitted to a deformation. The harvesting of the piezo-generated energy through a Schottky contact is depending on the establishment of the piezo-electric potential inside the nanostructures.
Polar-dopage-potentiel-relation.pngImpact of the GaN nanowire polarity on energy harvesting - Appl. Phys. Lett. 2014
From single III-nitride nanowires to piezoelectric generators: New route for powering nomad electronics – Semiconductor Science and Technology 2016

Energy harvesting efficiency in GaN nanowire: the critical influence of the Schottky nanocontact

The performances of 1D-nanostructure based nanogenerators are governed by the ability of nanostructures to efficiently convert mechanical deformation into electrical energy, and by the efficiency with which this piezo-generated energy is harvested. We have demonstrated that the harvesting efficiency of piezoelectric energy generated by GaN nanowires is strongly affected by Schottky nanocontact properties at interface with electrode.

Harvesting efficiency.pngEnergy harvesting efficiency in GaN nanowire-based nanogenerators: the critical influence of the Schottky nanocontact – Nanoscale 2017

GaN NWs based Piezo-generators :

The design of the Piezo-generator is based on GaN NWs having high piezoelectric response and takes into account of the relationship existing between the material properties and the piezoelectric generation mechanism. We demonstrate the first piezo-generator integrating vertical array of p-doped GaN NWs operating under compressive strain. The maximum power density delivers by the generator is of ~12.7 mW/cm3. This value states the new state of the art for nitride piezo-generators and opens the way for powering electronic devices, such as medical implants.
Piezo-Generator Integrating Vertical Array of GaN Nanowires Nanotechnology 2016
Nanotechnology Select

The flexibility is the key point enabling the conformal integration of generators on different objects with arbitrary shape. It is thus crucial to integrate the piezoelectric NWs onto soft flexible substrates. Flexible PGs.png
Nitride Nanowires: From Rigid to Flexible Piezo-generators

Connections :

- Guest editor Special Issue "Nanowire-based Piezo-Generators"
- GDR «Pulse» - Axis “Epitaxial systems properties and applications”
National Research Group PULSE dedicated to epitaxy of semiconductor systems with an in-depth understanding of the growth mechanisms and the development of innovative approach in order to allow major progress

Collaborations :

C2N : M. Tchernycheva & E. Lefeuvre
Geeps : P. Chrétien & F. Houzé
IEMN: Prof. E. Dogheche
INAC/CEA-Grenoble: Dr. J. Eymery
GPM: Dr. L. Rigutti
Cintra: Prof. P. Coquet, Prof. Wang Hong, Dr. M. D. Birowosuto
Students/Post-docs : L. Lu, N. Jegenyes, M. Morassi

Puce Publications dans des journaux

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