Disorder and the Optical-Absorption Edge of Hydrogenated Amorphous Silicon

Cody, George D.; Tiedje, T.; Abeles, B.; Brooks, B.; Goldstein, Y.

doi:10.1103/physrevlett.47.1480

Cited by 1,124 publications

(496 citation statements)

References 12 publications

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“…The exponents in the power law decay are around --0.3 in accordance with samples grown by other techniques [9]. Similar phenomena with different values for the power law index occur in amorphous semiconductors such as a-Si : H. As an explanation for the long times the presence of extended band tail states was invoked [10]. According to the multiple trapping model, thermal release times t rel of trapped carriers increase exponentially with the energetic distance of the trap level E T from the valence band edge E V :…”

Section: Resultssupporting

confidence: 57%

Low Temperature Photoluminescence, Transient Photoconductivity and Microwave Reflection for Optical Properties and Transport in PLD‐GaN

Niehus¹,

Sanguino²,

Schwarz³

et al. 2002

phys. stat. sol. (c)

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Optical and transport data on GaN samples grown by low-temperature pulsed laser deposition are presented. Large below-gap band tails are observed in optical absorption spectroscopy. The most intense photoluminescence lines of medium crystalline quality samples can be attributed to excitons bounded to stacking faults. The samples of the highest quality show, besides the ubiquitous yellow band, a large near band emission (NBE) peaking at 3.47 eV. The large width of the NBE is attributed to the joint effects of the band tails and an elevated carrier concentration. Secondary photocurrent transients show a slow decay reaching the millisecond time region for a variety of excitation wavelengths and intensities, with a power law decay exponent of around --0.3. The long times are attributed to the trapping of excess carriers in extended band tail states. From the comparison of photocurrent decay with excess carrier-induced microwave reflection it is concluded that the decay dynamics at the air/film and film/substrate interfaces are identical.Introduction GaN is one of the base materials for modern electronic and optoelectronic devices such as light emitting diodes (LEDs), solar blind UV detectors, laser diodes (LDs) or high-mobility electron transistors (HEMTs) [1]. Despite impressive technical advances, some basic materials issues remain to be resolved. One of these is the elevated density of unwanted impurities that appear in the material independently of the deposition technique. The metalorganic chemical vapour deposition (MOCVD) technique, for instance, relies always on a precursor gas that may introduce unwanted effects.We presented recently a new approach for depositing GaN films, a hybrid, two-step, low-temperature pulsed laser deposition (PLD) [2]. In this work we study the optical properties and transport in gallium nitride (GaN) deposited by this technique. Optical spectroscopy (transmission and photoluminescence measurements) and photoconductivity data are presented.

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Section: Resultssupporting

confidence: 57%

Low Temperature Photoluminescence, Transient Photoconductivity and Microwave Reflection for Optical Properties and Transport in PLD‐GaN

Niehus¹,

Sanguino²,

Schwarz³

et al. 2002

phys. stat. sol. (c)

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“…36,38 Larger values are only found in systems with defective short range order, lowered by coordination defects and/or network modier ions, as in hydrogenated Si, uori-nated silica, Si-doped AsGa, and Cu-doped CdS (X ¼ 2-8, 2-3, 17, and 8, respectively). 35,36,[38][39][40][41] The occurrence of such a high X value in g-Ga 2 O 3 NCs strongly points out the role of the interphase, which is likely responsible for a large amount of localized states caused by coordination mismatch and stoichiometry deviation. In fact, it is quite reasonable that band-to-band transitions are strongly inuenced by interphase properties, since the surface-to-volume ratio is very large.…”

Section: Resultsmentioning

confidence: 96%

“…2a), where E U is the Urbach energy which is related to the energy distribution of localized states at the edges of the energy gap. 35 Fig. 2a also shows the spectrum of a Ga-free reference sample.…”

Section: Resultsmentioning

confidence: 99%

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Light-emitting Ga-oxide nanocrystals in glass: a new paradigm for low-cost and robust UV-to-visible solar-blind converters and UV emitters

et al. 2014

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“…10 which shows that the 1 hour annealing at 793 K leads to a saturation their values. The progressive sharpening of the band edge which is observed with increasing heat treatments is to be ascribed to the progressive reduction of strain in the material which is known to affect the exponential absorption edge in semiconductors [12]. A reduction in strain, during the structural relaxation process in ion implanted a-Si, has in fact been detected by Raman spectroscopy measurements [6] and has also been related to the relaxation enthalpy detected by calorimetric measurements [6].…”

Section: T (K)mentioning

confidence: 89%

Optical absorption studies of ion implanted and amorphous silicon

et al. 1994

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Abstract.A detailed study of the implantation induced damage in Si on sapphire, carried out by optical absorption measurements extending from energies above the band gap down to energies far into the sub gap region of Si, is presented. The changes induced in the optical band gap, band edge slopes and in the sub gap features of the spectra are carefully described. The various stages of formation and quenching of divacancies were monitored as a function of implantation conditions and annealing cycles through their 1.8 pm absorption band. It is shown that the divacancies strongly affect the population of band tail states and the annealing studies revealed that the progressive quenching of the divacancy band is followed by the appearance of another absorption band, characteristic of some intrinsic secondary defect, whose annealing behaviour is similar to the one observed for the 5-vacancies EPR spectrum. The study of the structural relaxation process in implanted a-Si gave indications that the process is indeed associated with annihilation of defects as well as average strain reduction in the material, in agreement with earlier indications.

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Disorder and the Optical-Absorption Edge of Hydrogenated Amorphous Silicon

Cited by 1,124 publications

References 12 publications

Low Temperature Photoluminescence, Transient Photoconductivity and Microwave Reflection for Optical Properties and Transport in PLD‐GaN

Low Temperature Photoluminescence, Transient Photoconductivity and Microwave Reflection for Optical Properties and Transport in PLD‐GaN

Light-emitting Ga-oxide nanocrystals in glass: a new paradigm for low-cost and robust UV-to-visible solar-blind converters and UV emitters

Optical absorption studies of ion implanted and amorphous silicon

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