Stability of GaN films under intense MeV He ion irradiation

Schwarz, R.; Cabeça, R.; Morgado, E.; Niehus, M.; Ambacher, O.; Marques, C.; Alves, E.

doi:10.1016/j.diamond.2007.01.017

Cited by 3 publications

(2 citation statements)

References 9 publications

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“…[1][2][3][4] GaN is also a promising material for radiation hard particle detectors operating in harsh environment of irradiations. [5][6][7][8] To support the sufficient charge collection efficiency within a detector volume, the rather thick layers of detector base region should be used in design of the diode type particle detectors.…”

Section: Introductionmentioning

confidence: 99%

Study of carrier recombination transient characteristics in MOCVD grown GaN dependent on layer thickness

et al. 2013

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The MOCVD grown GaN epi-layers of different thickness have been examined in order to clarify a role of surface recombination, to separate an impact of radiative and non-radiative recombination and disorder factors. The microwave probed –photoconductivity (MW-PC) and spectrally resolved photo-luminescence (PL) transients were simultaneously recorded under ultraviolet (UV) light 354 nm pulsed 500 ps excitation. The MW-PC transients exhibited the carrier decay components associated with carrier decay within micro-crystals and the disordered structure on the periphery areas surrounding crystalline columns. Three PL bands were resolved within PL spectrum, namely, the exciton ascribed UV-PL band edge for hν>3.3 eV, blue B-PL band for 2.5 < hν < 3.0 eV and yellow Y-PL band with hν < 2.4 eV. It has been obtained that intensity of UV-PL band increases with excitation density, while intensity of B-PL band is nearly invariant. However, intensity of the Y-PL increases with reduction of the excitation density. The Y-PL can be associated with trapping centers. A reduction of UV excitation density leads to a decrease of the relative amplitude of the asymptotic component within the MW-PC transients and to an increase of the amplitude as well as duration of the yellow spectral band (Y-PL) asymptotic component. Fractional index α with values 0.5 < α < 0.8 was evaluated for the stretched-exponent component which fits the experimental transients determined by the disordered structure ascribed to the periphery areas surrounding the crystalline columns.

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Section: Introductionmentioning

confidence: 99%

Study of carrier recombination transient characteristics in MOCVD grown GaN dependent on layer thickness

et al. 2013

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“…We have previously looked at optoelectonic properties of irradiated GaN films prepared by pulsed laser deposition (PLD) and found that GaN shows somewhat higher radiation resistance [5] when compared to particle detectors based on amorphous silicon films [6,7] or crystalline silicon (c-Si) wafers [8].…”

Section: Introductionmentioning

confidence: 99%

Defects in Irradiated ZnO Thin Films Studied by Photoluminescence and Photoconductivity

Schwarz¹,

Ayouchi²,

Brandão³

et al. 2010

MRS Proc.

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Pulsed-laser-deposited ZnO thin films were exposed to a 1.5 MeV helium ion beam to study the changes in radiative and non-radiative recombination. We first measured photoluminescence (PL) spectra at 4.2 K excited with the 325 nm line of a HeCd laser. The asdeposited films showed a donor-bound exciton peak at 3.3567 eV attributed to Zn interstitials. After irradiation the donor-bound-exciton dominated PL spectra shifted to acceptor-bound behaviour with a signal at 3.3519 eV, tentatively attributed to Li or Na acceptors. In contrast to the approximately 30 % decrease of the PL signal near the band edge, we observed a strong concomitant enhancement of the green/orange PL band, located between 2.1 eV and 2.8 eV, by a factor of over 4. Candidates for those transitions are Li impurities and/or O vacancies. For comparison, the steady-state photocurrent decreased strongly in the irradiated region, which can also be attributed to increased non-radiative recombination through oxygen-related defects.

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Photoconductivity in organic thin films: From picoseconds to seconds after excitation

Day

Subramanian

Anthony

et al. 2008

Journal of Applied Physics

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We present a detailed study, on time scales from picoseconds to seconds, of transient and continuous wave (cw) photoconductivity in solution-grown thin films of functionalized pentacene (Pc), anthradithiophene (ADT), and dicyanomethylenedihydrofuran (DCDHF). In all films, at temperatures of 285–350 K, we observe fast carrier photogeneration and nonthermally activated charge transport on picosecond time scales. At ∼30 ps after photoexcitation at room temperature and at applied electric field of 1.2×104 V/cm, values obtained for the product of mobility and photogeneration efficiency, μη, in ADT-tri-isoproplysilylethynyl-(TIPS)-F, Pc-TIPS, and DCDHF films are ∼0.018–0.025, ∼0.01–0.022, and ∼0.002–0.004 cm2/V s, respectively, depending on the film quality, and are weakly electric field dependent. In functionalized ADT and Pc films, the power-law decay dynamics of the transient photoconductivity is observed, on time scales of up to ∼1 μs after photoexcitation, in the best samples. In contrast, in DCDHF amorphous glass, most of the photogenerated carriers are trapped within ∼200 ps. Transport of photoexcited carriers on longer time scales is probed by cw illumination through an optical chopper, with a variable chopper frequency. In contrast with what is observed on picosecond time scales, charge carriers on millisecond and longer time scales are predominantly localized, and are characterized by a broad distribution of carrier lifetimes. Such carriers make the principal contributions to dc photoconductivity.

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Stability of GaN films under intense MeV He ion irradiation

Cited by 3 publications

References 9 publications

Study of carrier recombination transient characteristics in MOCVD grown GaN dependent on layer thickness

Study of carrier recombination transient characteristics in MOCVD grown GaN dependent on layer thickness

Defects in Irradiated ZnO Thin Films Studied by Photoluminescence and Photoconductivity

Photoconductivity in organic thin films: From picoseconds to seconds after excitation

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