Non-equilibrium Charge Carriers Life Times in Semi-Insulating GaAs Compensated with Chromium

Zarubin, A.; Mokeev, D.Y.; Okaevich, L.S.; Tyazhev, A.; Bimatov, M.V.; Lelekov, M. A.; Ponomarev, I. A.

doi:10.1109/sibedm.2006.231988

Cited by 10 publications

(8 citation statements)

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“…Such a behavior was described earlier by other authors and assigned to the short lifetime of the non-collected charge carriers [25]. In agreement with these findings, the short lifetime of the holes in GaAs:Cr (which also has been mentioned previously in literature [18,21,24]) could be responsible for the observed crater effect: when a photon is absorbed close to the pixel electrode, a negative signal will be induced on the neighboring electrodes by the electrons drifting to the collecting electrode. Typically this negative signal is compensated by charge carriers of the opposite polarity (holes) drifting to the backside electrode.…”

Section: 'Crater Effect'supporting

confidence: 90%

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Characterization of GaAs:Cr sensors using the charge-integrating JUNGFRAU readout chip

et al. 2019

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A: Chromium compensated GaAs sensors have been characterized using the chargeintegrating readout chip JUNGFRAU. Due to its low noise performance and 75 × 75 µm 2 pixel size, JUNGFRAU enables a precise measurement of the charge (of either polarity) with a high spatial resolution.Several sensor parameters like dark current, noise and spectral performance as well as the charge transport properties of the electrons have been determined. The short lifetime of holes in GaAs:Cr gives rise to an effect where pixels adjacent to a pixel with a photon hit show a strong negative signal when being absorbed close to the readout electrode. This so-called 'crater effect' has been simulated and allows an estimation of the hole lifetime in GaAs:Cr.

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Section: 'Crater Effect'supporting

confidence: 90%

“…When reversing the polarity to measure the (µ • τ) product of the holes, no signal could be measured, presumably due to the short hole lifetime in GaAs:Cr [18,21,24].…”

Section: Charge Transport Propertiesmentioning

confidence: 99%

Characterization of GaAs:Cr sensors using the charge-integrating JUNGFRAU readout chip

et al. 2019

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“…As the simulations reveal, the negative tail of the correlation plot reacts sensitively to variations of the hole lifetime, while keeping the hole mobility at values typically reported for this material [ 8 , 26 ]. Therefore, the negative tails of the correlation plots were further investigated to determine the best agreement between experimental and simulated data by fitting the values of the summed pulse heights in the eight neighboring pixels as function of the energy in the central pixel using Gaussian fits ( Figure 7 , left).…”

Section: Resultsmentioning

confidence: 60%

Characterization of Chromium Compensated GaAs Sensors with the Charge-Integrating JUNGFRAU Readout Chip by Means of a Highly Collimated Pencil Beam

Greiffenberg

Andrä

Barten

et al. 2021

Sensors

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Chromium compensated GaAs or GaAs:Cr sensors provided by the Tomsk State University (Russia) were characterized using the low noise, charge integrating readout chip JUNGFRAU with a pixel pitch of 75 × 75 µm2 regarding its application as an X-ray detector at synchrotrons sources or FELs. Sensor properties such as dark current, resistivity, noise performance, spectral resolution capability and charge transport properties were measured and compared with results from a previous batch of GaAs:Cr sensors which were produced from wafers obtained from a different supplier. The properties of the sample from the later batch of sensors from 2017 show a resistivity of 1.69 × 109 Ω/cm, which is 47% higher compared to the previous batch from 2016. Moreover, its noise performance is 14% lower with a value of (101.65 ± 0.04) e- ENC and the resolution of a monochromatic 60 keV photo peak is significantly improved by 38% to a FWHM of 4.3%. Likely, this is due to improvements in charge collection, lower noise, and more homogeneous effective pixel size. In a previous work, a hole lifetime of 1.4 ns for GaAs:Cr sensors was determined for the sensors of the 2016 sensor batch, explaining the so-called “crater effect” which describes the occurrence of negative signals in the pixels around a pixel with a photon hit due to the missing hole contribution to the overall signal causing an incomplete signal induction. In this publication, the “crater effect” is further elaborated by measuring GaAs:Cr sensors using the sensors from 2017. The hole lifetime of these sensors was 2.5 ns. A focused photon beam was used to illuminate well defined positions along the pixels in order to corroborate the findings from the previous work and to further characterize the consequences of the “crater effect” on the detector operation.

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“…The NCC lifetime was estimated by means of experimental samples of Type 2 (figure 1) with a minimum gradient of the NCC lifetime. A detailed procedure employed to determine the mobility-lifetime products for electrons and holes is described elsewhere [5]. Low photocurrents in the near-surface layers of the detector material (figure 1) are due to short NCC lifetimes.…”

Section: Pulse Height Distributionmentioning

confidence: 99%

Chromium-compensated GaAs detector material and sensors

Budnitsky¹,

Tyazhev²,

Novikov³

et al. 2014

J. Inst.

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Results obtained from numerical calculations of and experimental studies on the pulse height distribution inherent in ionizing radiation gallium arsenide sensors as a function of the design features of the devices and electrophysical characteristics of the detector material are presented. It is shown that the pulse height distribution is defined by the distribution pattern of the nonequilibrium charge carrier lifetime and by the electric field profile in the bulk of the sensor. Investigations on the detector sensitivity to X-ray energies in the range between 40 and 150 keV were performed. The sensor polarization was found to produce only a marginal effect compensated by an increase in the bias voltage. Prototype pixel sensors measuring 256 × 256 and 512 × 768 pixels with a 55 µm pitch and a 500 µm thick sensitive layer were produced. The dependence of the photocurrent and count rate on the X-ray radiation intensity and bias voltage applied to the sensor was examined. In the 40-80 keV energy range, the maximum count rate amounted to 800 kHz/pixel for a negative sensor bias voltage of 800 V. The sensors are demonstrated to provide spatial resolution varying with the pixel pitch and to enable high-quality X-ray images to be obtained.

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Non-equilibrium Charge Carriers Life Times in Semi-Insulating GaAs Compensated with Chromium

Cited by 10 publications

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Characterization of GaAs:Cr sensors using the charge-integrating JUNGFRAU readout chip

Characterization of GaAs:Cr sensors using the charge-integrating JUNGFRAU readout chip

Characterization of Chromium Compensated GaAs Sensors with the Charge-Integrating JUNGFRAU Readout Chip by Means of a Highly Collimated Pencil Beam

Chromium-compensated GaAs detector material and sensors

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