Abstract
The operational characteristics of capacitor-type detectors based on HPHT and CVD diamond have been investigated using perpendicular and parallel injection of carrier domain regimes. Simulations of the drift-diffusion current transients have been implemented by using dynamic models based on Shockley-Ramo’s theorem, under injection of localized surface domains and of bulk charge carriers. The bipolar drift-diffusion regimes have been analyzed for the photo-induced bulk domain (packet) of excess carriers. The surface charge formation and polarization effects dependent on detector biasing voltage have been revealed. The screening effects ascribed to surface charge and to dynamics of extraction of the injected bulk excess carrier domain have been separated and explained. The parameters of drift mobility of the electrons μe = 4000 cm2/Vs and holes μh = 3800 cm2/Vs have been evaluated for CVD diamond using the perpendicular profiling of currents. The coefficient of carrier ambipolar diffusion Da = 97 cm2/s and the carrier recombination lifetime τR,CVD ≌ 110 ns in CVD diamond were extracted by combining analysis of the transients of the sensor current and the microwave probed photoconductivity. The carrier trapping with inherent lifetime τR,HPHT ≌ 2 ns prevails in HPHT diamond.
Highlights
Diamond is one of the most promising wide-gap materials for applications in the fabrication of high frequency sensors and radiation-tolerant particle detectors [1,2,3,4,5,6,7,8,9,10]
The operation dynamics and charge transport characteristics are traditionally examined by measurements of the transients of the injected charge drift current (ICDC) [13,15,18] and analysis of these characteristics [16,17,18,25,26] based on Shockley-Ramo’s theorem [27,28]
The non-linear absorption processes of two-photon via virtual states or two-step absorption through empty deep levels are most probable processes. It had been proved [35] that both two-photon and two-step processes compete in generation of excess carrier pairs in defect-rich high pressure high temperature (HPHT) diamond samples at elevated excitation intensities
Summary
Diamond is one of the most promising wide-gap materials for applications in the fabrication of high frequency sensors and radiation-tolerant particle detectors [1,2,3,4,5,6,7,8,9,10]. The dynamics of the polarization effect, which is commonly ascribed to ionized traps [16], have been revealed and their dependence on bias voltage as well as on bulk and localized excess carrier injection regime has been analyzed This polarization effect appeared to be significant in the range of rather low (
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