Impregnated Semiconductor Scintillator

Luryi, Serge

doi:10.1142/9789814273022_0019

Cited by 2 publications

(12 citation statements)

References 6 publications

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“…The "problem" is that we can obtain a reasonable fit also by assuming an exponential distribution (see footnote b above) with the length D L as an adjustable parameter [14]. For example, the 18 3 D 2 10 cm N − = × data for ( ) E R are well fit with D 45µm L = , cf. the exponential curve in Fig.…”

Section: Transmission and Reflection Luminescence Spectramentioning

confidence: 99%

“…We decided to explore the possibilities that would arise with an all-epitaxial fast-growth technique. This has led to our invention [18] described below.…”

Section: Layered Scintillator Based On Photon-assisted Transport Of Hmentioning

confidence: 99%

“…[18]. The scintillator body comprises a sequence of k barrier (InP) layers Bi of thickness b, alternating with k-1 well layers Wi of thickness w made of quaternary InGaAsP lattice-matched to InP.…”

Section: Layered Scintillator Based On Photon-assisted Transport Of Hmentioning

confidence: 99%

“…Our understanding of the anomalous transport of minority carriers in direct-gap semiconductor of high radiative efficiency has led to the invention [18] of a layered scintillator, described in Section 6. The idea of embedding radiation sites in a semiconductor (or insulator) material is nearly as old as the scintillator concept itself [19].…”

Section: Introductionmentioning

confidence: 99%

“…The density of the radiation sites must be very high, so that the typical travel distance for carriers is much smaller than their diffusion length. The novelty of our idea [18] is to employ the photon-assisted transport of minority carriers rather than their ordinary diffusion. This allows one to space out the radiation sites (in our case, narrow lowbandgap wells embedded in a wide-gap semiconductor matrix) by a large distance.…”

Section: Introductionmentioning

confidence: 99%

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LÉVY FLIGHT OF HOLES INInPSEMICONDUCTOR SCINTILLATOR

SUBASHIEV¹,

SUBASHIEV²

2013

Selected Topics in Electronics and Systems

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High radiative efficiency in moderately doped n-InP results in the transport of holes dominated by photon-assisted hopping, when radiative hole recombination at one spot produces a photon, whose interband absorption generates another hole, possibly far away. Due to "heavy tails" in the hop probability, this is a random walk with divergent diffusivity (process known as the Lévy flight). Our key evidence is derived from the ratio of transmitted and reflected luminescence spectra, measured in samples of different thicknesses. These experiments prove the non-exponential decay of the hole concentration from the initial photo-excitation spot. The power-law decay, characteristic of Lévy flights, is steep enough at short distances (steeper than an exponent) to fit the data for thin samples and slow enough at large distances to account for thick samples. The high radiative efficiency makes possible a semiconductor scintillator with efficient photon collection. It is rather unusual that the material is "opaque" at wavelengths of its own scintillation. Nevertheless, after repeated recycling most photons find their way to one of two photodiodes integrated on both sides of the semiconductor slab. We present an analytical model of photon collection in two-sided slab, which shows that the heavy tails of Lévy-flight transport lead to a high charge collection efficiency and hence high energy resolution. Finally, we discuss a possibility to increase the slab thickness while still quantifying the deposited energy and the interaction position within the slab. The idea is to use a layered semiconductor with photon-assisted collection of holes in narrow-bandgap layers spaced by distances far exceeding diffusion length. Holes collected in these radiative layers emit longwave radiation, to which the entire structure is transparent. Nearly-ideal calculated characteristics of a mm-thick layered scintillator can be scaled up to several centimeters.

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Section: Transmission and Reflection Luminescence Spectramentioning

confidence: 99%

“…We decided to explore the possibilities that would arise with an all-epitaxial fast-growth technique. This has led to our invention [18] described below.…”

Section: Layered Scintillator Based On Photon-assisted Transport Of Hmentioning

confidence: 99%

Section: Layered Scintillator Based On Photon-assisted Transport Of Hmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

LÉVY FLIGHT OF HOLES INInPSEMICONDUCTOR SCINTILLATOR

SUBASHIEV¹,

SUBASHIEV²

2013

Selected Topics in Electronics and Systems

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LÉVY FLIGHT OF HOLES IN InP SEMICONDUCTOR SCINTILLATOR

Luryi

Subashiev

2012

Int. J. Hi. Spe. Ele. Syst.

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also seem to follow Lévy flights when foraging [11]. Finally, a vast literature is devoted to Lévy flights in finance, "random walk down the Street" [12].Nevertheless, there have been preciously few experimentally available laboratory systems for studying LF transport, ideally with variable parameters. A rather ingenious such system was recently demonstrated by Barthelemy et al. [13], who embedded scattering particles in a glass matrix -together with non-scattering glass microspheres of same refractive index as the matrix. The sole purpose of these spacer spheres was to modify locally the average separation between the scattering particles and thus control the step-length distribution for photon transport. With specially designed, highly non-trivial, distributions of microspheres diameter, the authors were able to observe a Lévy flight of light.Recently, we described [14] a more "natural" lab system exhibiting Lévy flight, namely the direct-gap semiconductor of high radiative efficiency, specifically n-doped InP. The randomly walking particles in this case are minority carriers (holes) and their dominant transport process is photon-assisted hopping. This process, also known as the photon recycling, consists of radiative recombination of a hole at one spot producing a photon, whose subsequent interband absorption leads to the re-emergence of a hole at another spot, possibly far away. The high radiative efficiency and low free-carrier absorption of light in lightly doped InP ensure that photon recycling continues for about 100 times before a hole recombines non-radiatively or a photon is absorbed without leaving a hole behind. The randomness of free flight is set by the emission spectrum in radiative recombination. This spectrum, combined with the interband absorption probability and the probability of photon propagation to a given distance, defines the probability distribution for free flights of photons. Photons generated in the long-wavelength wing of the emission spectrum travel long distances before they get re-absorbed and are responsible for the divergent variance of the distribution and the Lévy-flight nature of the resulting random walk. This process is reviewed in Sect. 2.Manifestations of anomalous transport were found [14] by studying photoluminescence in ndoped InP. The key evidence was derived from the ratio of transmitted and reflected luminescence spectra, measured in samples of the same doping level but very different thicknesses (350 µm vs. 50 µm). The results give a direct experimental proof of the nonexponential decay of the minority-carrier concentration from the surface where the holes were photo-excited initially. The power-law decay of the hole concentration, characteristic of the LF transport, is steep enough at short distances (steeper than an exponent) to fit the data for the thin sample, and at the same time slow enough at large distances (again, compared to an exponent) to account for the data for thick samples. This work is reviewed in Sect. 3. Transport at much larger distances (up to...

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Impregnated Semiconductor Scintillator

Cited by 2 publications

References 6 publications

LÉVY FLIGHT OF HOLES INInPSEMICONDUCTOR SCINTILLATOR

LÉVY FLIGHT OF HOLES INInPSEMICONDUCTOR SCINTILLATOR

LÉVY FLIGHT OF HOLES IN InP SEMICONDUCTOR SCINTILLATOR

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