Symposium C2.2: Interface Design and Modelling affiliations date Numerical and experimental ongoing on III-V/Si high-efficiency tandem solar cell M. Da Silva1, S. Wang1, S. Almosni1, C. Cornet1, A. Létoublon1, C. Levallois1, A. Rolland1, J. Even1, L. Pedesseau1, P. Rale2, L. Lombez2, J.-F. Guillemoles2,3, and O. Durand1 UEB, INSA, FOTON, UMR CNRS 6082, Rennes, France IRDEP, UMR 7174 - CNRS-EDF-ENSCP, EDF R&D, Chatou, France NextPV, LIA CNRS-RCAST/U. Tokyo-U. Bordeaux, 4-6-1 Komaba, Meguro-ku, Tokyo, Japan EUROMAT 2015: Symposium C2.2: Interface Design and Modelling 23 September 2015

Outline Motivation GaP/Si: crystal growth developments, issues and strategies GaP/Si: devices Photovoltaics Conclusion & Prospects

Motivation: III-V on silicon, many promises III-V/Si -Electronics Si -HEMT technology -Health/environment -Lab on chip applications -Integrated Biosensors Liang et al., Nature photonics 167, 511 (2010). Intel © -Energy -Low cost and mature technology -Limited mobility -Indirect bandgap -Photovoltaics -Thermoelectricity -Photonics -Single low cost photonics devices (lasers, LEDs, telecom devices) -Optical interconnects, on/off-chip

Motivation: Heterogeneous vs Monolithic Monolithic integration Heterogeneous integration III-V or IV growth on Si -group IV : Si-Raman lasers , strained Ge -group III-V devices on Si or SiGe (metamorphic or pseudomorphic) Bonding methods -Dies or wafers -InP and GaAs platforms -Si/SiO2 passive photonics Maturity Substrate costs alignments Thermal management

Motivation: The pseudomorphic approach 5 Pseudomorphic growth FOTON-OHM and CEMES (unpublished) GaP Metamorphic growth Δa/a=0,37%@RT dislocations engineering Si 28/11/2013 GaP/Si interface by HRTEM Quasi lattice-matching S.H.Huang et al., Appl. Phys. Lett. 93, 071102 (2008)

Motivation: Multijunction solar cells on silicon 6 -High efficiency solar cells on low cost/scalable Si substrate Applications Current matching ISS Space Weight/power < usual MJSC 1.7 eV (GaP-based) 1.1 eV (Si) CPV central Scalability J F Geisz and D J Friedman, Semicond. Sci. Technol. 17 (2002) 769–777 0.2-0.5 € / Wp Lattice-matched

GaP/Si: crystal growth developments, issues and strategies 7 GaP/Si: crystal growth developments, issues and strategies

Issues and strategies 3D growth of GaP on Si (surface energies) 8 3D growth of GaP on Si (surface energies) -alternated growth Ga-P-Ga-P-Ga … Micro-Twins, generated at the GaP/Si interface -Clean interface (contaminants-free) -Influence of the first monolayer of GaP Antiphase domains -silicon bisteps -initial Ga or P coverage

9 GaP/Si: devices

GaAs0.1P0.88N0.02 : a lattice-matched alloy GaP/Si: devices 10 The lattice-matched GaAsPN absorber S. Almosni et al., J. Appl. Phys. 113, 123509 (2013) S. Ilahi et al., Sol. Ener. Mat. and Sol. Cells. 141, 291 (2015) GaAs0.1P0.88N0.02 : a lattice-matched alloy Absorption around 1.8 eV

Efficiency far from the 15% expected GaP/Si: devices 11 PV solar cells on GaP substrate Device I-V under AM1.5G Efficiency far from the 15% expected  Influence of absorber thickness : issue of carrier collection in dilute nitrides ? S. Almosni et al., in preparation (2015)

Additional Shunt resistances BUT Good control of the GaP/Si interface GaP/Si: devices 12 PV solar cells on Si substrate Device I-V under AM1.5G GaPp Absorber GaPn GaP buffer Si substrate Additional Shunt resistances BUT Good control of the GaP/Si interface Prospects  Better carrier diffusion length in dilute nitrides alloys  GaP(n++)/Si(p++) : the best tunnel configuration ?

GaP/Si: devices: Tunnel Junction, modeling 13 A. Rolland et al., Opt. Quant. Electron. (2014) (a) Schematic of the GaAsPN/Si tandem cell and (b) Simulated current-voltage characteristic of a GaP(n+)/Si(p+) and Si(n+)/Si(p+) tunnel junctions at uniform doping of ~5x1019cm-3

GaP/Si: devices: Tunnel Junction, modeling 14 A. Rolland et al., Opt. Quant. Electron. (2014) Simulated Band diagram of a GaP(n+)/Si(p+) and Si(n+)/Si(p+) tunnel junctions at uniform doping of 1020 cm-3 at thermal equilibrium.

GaP/Si: devices: Top Cell, modeling 15 A. Rolland et al., Opt. Quant. Electron. (2014) Current voltage characteristic of the GaP/GaAsPN/GaP cell for GaAsPN layer thicknesses ranging from 0.5 µm to 3 µm..

Summary 16 Low density of planar defects, and annihilated antiphase boundaries Single GaAsPN solar cell grown on silicon Material optimization is still needed to improve carrier mobilities and lifetimes.

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