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Hydrogen in Semiconductors: Passivation and Nano-Engineering

This article explores the effects of hydrogen in semiconductors, including shallow and deep defect passivation, similarities to nitride passivation, and potential applications in band-gap and photonic crystal nano-engineering. It also discusses the significance of hydrogen in achieving Nobel prize-winning research.

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Hydrogen in Semiconductors: Passivation and Nano-Engineering

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  1. Anever-endingstory: Hydrogen in semiconductors M. Capizzi CNISM and Dipartimento di Fisica, Università “La Sapienza”, Roma, Italia

  2. First evidence of H related effects 1950–1st International Conference on the Physics of Semiconductors (Reading, UK) 1954– ZnO conductivity is found to increase upon H diffusion into the crystal 2000– H-O bond formation gives rise to donor levels and accounts for the conductivity increase Zeit. Phys. 138, 478 (1954)

  3. Outline • Why (investigating H)? • Shallow and deep defect passivation by hydrogen • Are full and dilute nitride passivation casessimilar? • An in-planeband-gap and photonic crystal nano-engineering • Conclusions and perspectives

  4. Why H? Present in most sample growth techniques (LPE, VPE, MOVPE, MBE) and in device making processes The smallest and most highly reactive atom, with high diffusivity D (10-4 cm2s-1 @ 1400 K) insemiconducting materials Although H has been often considered “essentially unreactive”, it may be relevant to verify if and when this statement may fail

  5. Why (investigating H)? • Shallow and deep defect passivation by hydrogen • Are full and dilute nitride passivation casessimilar? • An in-planeband-gap and photonic crystal nano-engineering • Conclusions and perspectives

  6. 1976:n- and p-typehydrogenateda-Si are grown byrfsputteringlow costsolarcells A. J. Paul et al., Sol. State Comm. 20, 969 (1976) 1954-1985: A short H summary 1956: Very low H solubility in Si and Ge (1014 cm-3), evenat high T(1400 K) A. Van Wieringen and N. Warmoltz, Physica 22, 849 (1956) A 20-years long hibernation 1974: Highquality a-Si films were grown by rf dissociation of SiH4: lower trap density in the band gap P. G. Le Comber et al., Proc. 5th ICALS, 1974, p. 245 W. E. Spear et al., Proc. 5th ICALS, 1974, p. 1 1978: His introduced and reversibly taken out from samples by thermal annealing J. I. Pankove, Appl. Phys. Lett. 32, 812 (1978) 1985: IR spectra indicate that B passivation by H was due to strong Si-H bonds J. I. Pankove, P. J. Zanzucchi, C. W. Magee, and G. Lucovsky, Appl. Phys. Lett. 46, 421 (1985)

  7. 1954-85: Conclusions Hstrongly binds to dangling bonds and localized charges In Si, Ge, GaAs, GaP: H+passivates the electrical activity of acceptors, H- that of donors, by forming mono-H complexes H stable charge state depends on Fermi energy H has an amphoteric behavior C. G. Van de Walle and J.Neugebauer, Hydrogen in semiconductors, Annu. Rev. Mater. Res. 36, 179 (2006) J. I. Pankove and N. M. Johnson, Hydrogen in Semiconductors, Semiconductors and Semimetals v. 34, R. K. Willardson and A. C. Beer eds. (Academic Press, Boston, 1991) S. J. Pearton, J. W. Corbett, and M. Stavola, Hydrogen in Crystalline Semiconductors, Materials Science, H.J. Queisser ed. (Springer-Verlag, Berlin, 1992)

  8. 2014: How the control of H may lead to a Nobel prize A novel growth method: Two-Flow MOVPE (N2++H2) and (TMG+NH3+H2) Reproducible, uniform, high quality (mobility) undoped GaN S. Nakamura et al., Appl. Phys. Lett. 58, 2021 (1991) S. Nakamura, Jpn. J. Appl. Phys. 30, L1705 (1991) However, acceptor (Mg) concentrations were orders of magnitude lower than doping, hindering the achievement of highly doped p-n junctions (and LEDs)

  9. 2014: How the control of H may lead to a Nobel prize As grown MOVPE GaN samples contain significant H concentrations that effectively passivate Mg acceptors S. Nakamura et al., Jpn. J. Appl. Phys. 31, L139 (1992) S. Nakamura et al., Jpn. J. Appl. Phys., 31 1258 (1992) Thermal annealing at T > 700 C in N2 release H+ from its bond with Mg highly doped p-type GaN Ga Mg H N Industrial Process Compatible for GaN (and InGaN) LEDS http://www.nobelprize.org/nobel_prizes/physics/laureates/2014/nakamura-lecture.html

  10. 1983…….2015:H in our laboratory 1983: a-Si by double Kaufman ion-gun: - Si sputtering with Ar - defect passivation by H rf plasma produces a better a-Si,… but Kaufman is betterthan rf plasma wrt a controlled and reproducible H-irradiation of semiconductor

  11. combined with IR measurements of H reorentation under stress give the first evidence of quantum effects (zero-point energy) ruling low-T H diffusion Y. M. Cheng and M. Stavola, Phys. Rev. Lett.73, 3419 (1994) Anelastic relaxation measurements G. Cannelli, R. Cantelli, M. Capizzi, C. Coluzza, F. Cordero, A. Frova, and A. Lo Presi, Phys. Rev. B 44, 11486 (1991) H quantum diffusion aslater supported by measurements in GaAs:Zn G. Cannelli, R. Cantelli, F. Cordero, E. Giovine, F. Trequattrini, M. Capizzi, and A. Frova, "Quantum diffusion of deuterium around substitutional Zn in GaAs” Solid State Commun. 98, 873 (1996)

  12. Why (investigating H)? • Shallow and deep defect passivation by hydrogen • Are full and dilute nitride passivation casessimilar? • An in-planeband-gap and photonic crystal nano-engineering • Conclusions and perspectives

  13. In(AsN)/ donor complexes In(AsN) / H-N (?) donors Hydrogenation of InAs increases PL efficiency passivation of n-r defects [H0] =1×1016 ionscm-2 [N]=0.02% band filling Hydrogenation of In(AsN) increases carrier density donor formation [N]  0.02% Hydrogenation of In(AsN) increases carrier density (already for small amounts of N substitutional atoms) S. Birindelli,………and M. Capizzi, Semicon. Sci. Technol. 30, 105030 (2015)

  14. H-N donors in In(AsN) Raman scattering shows a decrease in the intensity of some N related vibrational modes upon hydrogenation H-N complexes At annealing temperatures T(500-600) K, H atoms begin to desorb from In(AsN), at higher T’s, N atomsdesorb and Eg increases Eg and EF from lineshape fits EFmax=0.25 eV nmax=7×1018 cm-3 for [N]= 1.8×1020 cm-3 Fermi stabilization energy EFS (4.65-4.8) eV below vacuum level (**) S. Birindelli,………and M. Capizzi, Semicon. Sci. Technol. 30, 105030 (2015) (*) W. Zawadzki, S. Klahn, and U. Merkt, Phys. Rev. Lett. 55, 983 (1985) (**) W. Walukiewicz, Phys. Rev. B 37, 4760 (1988)

  15. In N In N HAB HBC H donors in InN (and ZnO) Thermal annealing dH=z=1×1015 ions/cm2 First, donor concentration increases upon hydrogenation, then it decreases progressively with thermal annealing G. Pettinari, M. Capizzi, M. Capizzi, A. Polimeni et al., Phys. Rev. B 77, 125207 (2008) M. De Luca et al., Phys. Rev. B 86, 201202 (R) (2012)

  16. H and dilute nitrides TheTaming- byHydrogen - of the ChurlishNitrogen (may an alchemist’s dream come true?)

  17. Highest electronegativy among V-group atoms: Strong perturbationwhen N substitutes another group V atom Electronegativity The smallest V-group atom: Strong lattice mismatch Atomic radius N: A peculiar isoelectronic impurity Break down of the mean field approximation (VCA) and Vegard’s law

  18. Dilutenitrides: the Ga(AsN) case Electron charge density accumulates on the N atom with a breaking of the lattice translational simmetry P.R.C. Kent and A. Zunger, Phys. Rev. Lett. 86,2613 (2000) In the N isoelectronic impurity limit, for increasing N concentration: - Bandgapdecreases - Lattice constant increases - Electron effective mass shows ananomalous behavior Ga(AsN) untreated hydrogenated bowing ~ 20 eV - Optoelectronics devices - THz devices

  19. untreated hydrogenated BAC The heuristic Band Anti-Crossing (BAC) model F. Masia et al., Phys. Rev. B73, 73201 (2006) W. Shan et al. , Phys Rev. Lett.82, 1221 (1999) Host CBandsingle nitrogenlevel have a same symmetry (A): they repel each other and give rise to two new hybridized states, E+ and E- Interaction matrix element VMN increases with [N] E+ and E- symmetricallydepend on [N] E- and m* smoothlydepend on [N] The model reproduces well the energy gap dependence on [N] badly the effective massanomalousdependence on [N]

  20. N triplets cross CBM N pairs cross CBM LCINS theory BAC LCINS: ModifiedBACmodel LCINS, Linear Combinations of Isolated N States,extends the BAC model by taking into account single and cluster N states A. Lindsay and E.P. O’Reilly, Phys. Rev. Lett. 93, 196402 (2004) F. Masia et al., Phys. Rev. B73, 73201 (2006) Ga(AsN) me* estimated in a 3-band k∙p Ga(AsN) untreated hydrogenated Theory (even too)well reproducesN dependence for x 0.6%

  21. Ga(AsN) band-gap modulation by H A. Polimeni, G. Baldassarri Höger von Högersthal, F. Masia, M. Capizzi, A. Frova, S. Sanna, V. Fiorentini, P. J. Klar, and W. Stolz, Phys. Rev. B 69, 041201 (R) (2004) A. Polimeni, G. Baldassarri H. v. H., M. Bissiri, M. Capizzi, M. Fischer, M. Reinhardt, and A. Forchel: Phys. Rev. B 63, 201304 (R) (2001); Appl. Phys. Lett. 78, 3472-3474 (2001)

  22. N H D N-2H (canted) Nitrogen-di-hydrogencomplexes N H H IR absorption measurements in hydrogenated and/or deuterated Ga(AsN) as well as XANES measurements support a two-H complex with C1h-symmetry Mao-Hua Du et al., Phys. Rev. B 72, 73202 (2005) W. Beall Fowler et al., Phys. Rev. B 72, 35208 (2005) A. Amore Bonapasta et al., Phys. Rev. B 68, 115202 (2003) Fan Jiang et al., Phys. Rev. B 69, 041309 (R) (2004) G. Ciatto et al., Phys. Rev. B 71, 201301(R) (2005)

  23. GaP1-xNxx = 0.81% no H [H]=1018 cm-2 [H]=2 1018 cm-2 Alighteningapplication: Hydrogenated Ga(PN) Ga(PN) LED traffic light A. Polimeni et al., Phys. Rev. B 67, 201303(R) (2003)

  24. Why (investigating H)? • Shallow and deep defect passivation by hydrogen • Are full and dilute nitride passivation casessimilar? • An in-planeband-gap and photonic crystal nano-engineering • Conclusions and perspectives

  25. anovelrouteto top-down band-gap nanoengineering in the material growth plane Top-down in-plane band-gap nanoengineering Hydrogen modifies the whole electronic and structural properties of dilute nitrides in a fully tunable manner • The achievement of a • spatial control of hydrogen irradiation • spatial control of hydrogen removal • very sharp H diffusion forefront • allowed us to develop

  26. Hydrogen diffusion in presence of strong trapping • Thesharpnessof the D forefront increases with • increasing [N] • decreasing TD within 5 nm/decade @ 300 °C Fits of the SIMS profiles (red lines) provide H diffusion coefficients R. Trotta et al., Phys. Rev. B 80, 195206 (2009) R. Trotta et al., Adv. Materials 23, 2706 (2011). R. Trotta et al., Adv. Funct. Materials (Feature article) 22, 1782 (2012) to be used in modelling H diffusion

  27. Micro-PL GaAs laser laser GaAs Ga(AsN) 3mm EgGaAs EgGa(AsN) GaAs Ga(AsN) Ga(AsN) hydrogenated GaAs Band gap nanoengineering: Quantum wires M. Felici et al., Advanced Materials18, 1993 (2006) 500 nm nanowires Fabrication of a planar heterostructure

  28. Band gap nanoengineering: Quantum wires

  29. Band gap nanoengineering: Quantum dots single dot mPL d=80 nm ensemble 5 mm R. Trotta et al., Adv. Mat. (2011)

  30. Band gap nanoengineering: Quantum dots A strong antibunching is observed in the second order autocorrelation function of the QD emission line

  31. Band gap nanoengineering: Laser writing laser power Pa = 7 mW exposure times ta = 150, 120, 50 s l=633 nm 300 K mPL intensity maps H-shaped emitting area written by laser Pa = 15 mW ta = 10 s l=633 nm mapped at 300K by laser Pa = 0.1 mW Dependence of peak energy, EQW, of the Ga(AsN on annealing laser power Pa and duration ta at 300K ( = 633 nm). EQWin the V, untreated, sample is given by the horizontal dashed line.

  32. GaAsN dot hydrogenated GaAsN barriers Perspectives Tailor-made Ga(AsN) nanostructures Q rings Embedded QDs: In progress Photonic crystal cavities embedding Ga(AsN) nanostructures: In progress

  33. A novel H effect in InN For H doses dH 8×1015cm-2, the carrier concentration n increases, with very minor changes in Eg (blue arrows) For H doses dH (850)1015cm-2, the carrier concentration n decreases (1/4), with a huge (0.5 eV) increase in Eg (blue arrows) For H doses dH≥ 50×1015cm-2, the carrier concentration n increases slightly, with very minor changes in Eg (blue arrows), as in the H dose regime These results are supported by conductivity s measurements (notice the ¼ decrease in n in the intermediate regime) Thermal annealing almost restores the properties of the untreated samples G. Pettinari et al., Adv. Funct. Mater. 25, 5353 (2015)

  34. Solitary In* cations in InN HBC-3Hab : A novel four H (-N) complex The In atom at the center of the 4H-N complex is fully isolated: A solitary In* cation The In* level falls from the conduction band into the valence band (red curve) The repulsive interaction between the In* level and the bottom of the CB opens the gap G. Pettinari et al., Adv. Funct. Mater. 25, 5353 (2015)

  35. H in dilute nitrides: Conclusions • Hydrogen sweeps defects away from the energy gap of semiconductors • by formjng mono-hydrideswith • “shallow” and “deep” impurities • dangling bonds of vacancies or surface states • thus “transmuting” boron (and phosphorus) into “silicon” Hydrogen sweeps N level away from the conduction band of diluted nitrides by forming di-hydrogen complexes thus“transmuting” nitrogen into “arsenic” Four hydrogen atoms isolate an In atom (In*) from its four nearest neighbors N atoms, thus increasing by 0.4 eV the band gap of InN Hydrogenation through metallic masks prepared by EBL: a novel band-gap nanoengineeringin the growth plane of diluted nitrides and InN

  36. 51 years after their first discovery, effects H has in semiconductors will still be able to surprise us? Thank you for your attention!!!

  37. Main contributors from our laboratory G. Baldassarri S. Birindelli M. Bissiri M. De Luca M. Felici A. Frova F. Masia A. Mittiga A. Patanè G. Pettinari A. Polimeni R. Trotta

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