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Semiconductor Materials

Session chair: Kim , Kihyun (Korea University, Department of Radiologic Science, Seoul, South Korea); Erickson , Anna S. (Georgia Institute of Technology, Woodruff School of Mechanical Engineering, Nuclear and Radiological Engineering, Atlanta, USA)
Shortcut: R-08
Date: Thursday, 21 October, 2021, 9:15 AM - 11:15 AM
Room: RTSD
Session type: RTSD Session


Click on an contribution to preview the abstract content.

9:15 AM R-08-01

Characterization of virtual Frisch grid detectors fabricated from as-grown CdZnTeSe ingot (#1093)

U. Roy1, G. Camarda2, Y. Cui2, G. Yang3, R. James1

1 Savannah River National Laboratory, Aiken, South Carolina, United States of America
2 Brookhaven National Laboratory, Upton, New York, United States of America
3 North Carolina State University, Raleigh, North Carolina, United States of America


Over the past few years CdZnTeSe (CZTS) has emerged as an alternate material to replace CZT at a lower cost of production without compromising device performance. An ideal semiconductor material for room-temperature radiation detector applications should possess much less defects and higher compositional uniformity than CZT. A lower concentration of intrinsic defects and higher compositional uniformity in the resulting material ensure better spatial charge transport uniformity over large-volume detectors. This requirement of uniform spatial charge transport properties is a stringent one to enhance the yield of high-quality detectors, and CZT does not fully satisfy this requirement due to a random distribution of sub-grain boundary networks and Te inclusions in the crystals. The addition of selenium in the CZT matrix successfully avoids many of these issues and makes the resulting CZTS material promising as a potential replacement to CZT. The resulting quaternary material CZTS was found to be free from sub-grain boundary networks and also possess very few Te inclusions with better compositional uniformity along the length of the ingot, as compared to CZT grown by the Traveling Heater Method (THM). In this presentation we report detailed characterization of the performance of virtual Frisch grid detectors and their compositional uniformity for CZTS detectors fabricated from THM-grown ingots.

Keywords: II-VI semiconductor, Radiation detector
9:30 AM R-08-02

Effects of Surface Passivation on CdZnTeSe Nuclear Detectors (#1417)

S. U. Egarievwe1, 2, U. N. Roy2, 7, E. O. Agbalagba3, A. H. Davis4, M. B. Israel5, P. L. Alexander6, R. B. James7

1 Alabama A&M University, Nuclear Engineering and Radiological Science Center, Huntsville, Alabama, United States of America
2 Brookhaven National Laboratory, Nonproliferation and National Security, Upton, New York, United States of America
3 Federal University of Petroleum Resources, Department of Physics, Effurun, Nigeria
4 Stanford University, Bioengineering, Stanford, California, United States of America
5 University of South Alabama, Electrical and Computer Engineering, Mobile, Alabama, United States of America
6 Alabama A&M University, Biological and Environmental Sciences, Huntsville, Alabama, United States of America
7 Savannah River National Laboratory, Science and Technology, Aiken, South Carolina, United States of America


Cadmium zinc telluride selenide (CdZnTeSe) has shown great promise in reducing the cost of semiconductor nuclear detectors that are capable of operating at room temperature without cryogenic cooling. This is due to the high yield of detector-grade materials in the CdZnTeSe crystal growth process, which can be attributed to the much smaller numbers of Te inclusions and grain boundary network in CdZnTeSe compared to other CdTe-based semiconductors such as CdZnTe. In the present work, we study the effects of surface passivation on CdZnTe detectors using a mixture of ammonium fluoride and hydrogen peroxide solution (NH4F + H2O2 + H2O). Detectors fabricated from CdZnTeSe crystals showed very good energy resolutions: 1.1% for the 662-keV gamma peak of 137Cs by Frisch-grid detectors, and 5.9% for the 59.6-keV gamma peak of 241Am by planar detectors. Experimental results show that the leakage current is increased immediately after passivation and then decreases as the surfaces stabilizes. The resistivity of the CdZnTeSe is of the order of . The surface passivation improved the energy resolution of planar detector by 18% for the 59.6-keV gamma peak of 241Am.

AcknowledgmentThis work was supported in part by the National Science Foundation (NSF) Major Research Instrumentation (MRI) through award number 1726901; in part by U.S. Department of Energy (DOE), Office of Defense Nuclear Nonproliferation Research and Development, the DNN R&D (NA-22), and DOE NNSA MSIPP award number DE-NA0003980; in part by the U.S. Nuclear Regulatory Commission (NRC) through award 31310018M0035; in part by the U.S. Department of Homeland Security, Domestic Nuclear Detection Office through award number 2012-DN-077-ARI065-05; and in part by the NSF HBCU-UP Program through award number 1818732.
Keywords: CdZnTeSe, Chemical passivation, Frisch-grid detectors, Gamma rays, Nuclear detectors
9:45 AM R-08-03

A Study of Bandgap Defects in CsPbBr3 Single Crystals (#1419)

R. Toufanian1, P. Becla1, A. Datta1, S. Swain1, S. Motakef1

1 CapeSym, Inc., R&D, Natick, Massachusetts, United States of America


The unique optoelectronic properties of lead halide perovskite semiconductors has caused a surge of interest in their development as radiation detectors. In spite of recent advances in their performance, single crystals of all-inorganic CsPbBr3 are limited by the presence of intrinsic point defects within their lattice structure. In this study, these defects are identified in both vertical Bridgman and solution grown CsPbBr3 single crystals through photo-induced current transient spectroscopy (PICTS), and their defect charge transition levels and concentrations are determined.  A one-on-one comparison of melt and solution grown CsPbBr3 single crystals provides valuable insight into the influence of growth conditions on shallow and deep level electon and hole traps, and their effect on γ-radiation detection.


This material is based upon work supported by the U.S. Department of Energy, Office of DNN R&D Award Number DE-SC0020900.

Keywords: Lead halide perovskites, intrinsic point defects, defect formation energy, melt grown CsPbBr3, solution grown CsPbBr3
10:00 AM R-08-04

The Effect of Post-Growth Thermal Annealing on CdZnTe Crystals Grown by Vertical Gradient Freeze Technique (#606)

M. Ünal1, 2, O. B. Balbaşı1, 3, M. C. Karaman1, 3, A. M. Ünalan1, 4, G. Çelik1, 4, M. Parlak1, 3, R. Turan1, 4

1 Middle East Technical University, Crystal Growth Laboratory, Ankara, Turkey
2 Middle East Technical University, Micro and Nanotechnology Program of Graduate School of Natural and Applied Sciences, Ankara, Turkey
3 Middle East Technical University, Physics Department, Ankara, Turkey
4 Middle East Technical University, The Center for Solar Energy Research and Applications, Ankara, Turkey


Te inclusions are the main performance degrading defects in CdZnTe crystals. Because of the unique properties of CdZnTe, it is not possible to entirely eliminate Te inclusions during growth process. However, thermal annealing could decrease the concentration of Te inclusions by dissolving or migrating them at high temperatures. Annealing under Cd atmosphere could dissolve Te inclusions by implementing Cd atoms into CdZnTe crystals and compensating excess Te atoms inside of inclusions. However, implemented Cd atoms can form interstitial Cd defects easily; thus, annealing under Te atmosphere is needed to eliminate intestinal Cd formed by Cd-annealing. In this study, annealing under different atmospheres is studied and changes in Te inclusion concentrations are observed for different crystals. Additionally, it is observed that the resistivity of crystals decreases significantly after Cd-annealing, which is restored with Te-annealing.

Keywords: crystalline materials, semiconductor detectors, semiconductor growth, semiconductor radiation detectors, tellurium.
10:15 AM R-08-05

Exploring the Photoconductive Nature of Carbon Nanotube Ionizing Radiation Detectors (#581)

A. Rajapakse1, A. Erickson1

1 Georgia Institute of Technology, Nuclear and Radiological and Medical Physics, Atlanta, Georgia, United States of America


Carbon nanotubes (CNTs) are used extensively in sensing applications due to their electronic properties such as the ability to tune their conductance via an external electric field. This characteristic has led to their limited application in radiation detection where CNTs sense the charge carriers generated by ionizing radiation in a traditional semiconductor substrate. In this work, a vertically aligned CNT-based radiation detector was designed and fabricated around the concept of a field effect transistor (FET) geometry where the CNTs function as the device channel and the oxide/semiconductor substrate serve as a radiation absorber. The first iteration of the device responded weakly to the presence of ionizing radiation such as diagnostic x-rays. A complete overhaul of the fabrication process and rigorous CNT processing has led to dramatically improved device response in subsequent iterations. For example, these newer devices can discriminate between various doses when irradiated by an x-ray source i.e., discriminate between varying the tube voltage (energy) and tube current (number of x-rays). While the current work still focuses on device development and refinement, other aspects of the CNT-based detector functionality are also being explored. Recent device characterization has shown the ability of the device to behave as a broadband photoconductor to the wavelength range of 300 nm to 1100 nm without any modifications. The dual-function nature of the CNT-based detector can expand the application of this novel detector in any field requiring devices that demonstrate damage resistance, low power operation, and scalable detection areas.


This material is based upon work supported by the Department of Energy / National Nuclear Security Administration under Award Number(s) DE-NA0003921. This report was prepared as an account of work sponsored by an agency of the United States Government.

Keywords: Carbon Nanotube, Photoconductivity, Detector
10:30 AM R-08-06

Noise spectroscopy study of methylammonium lead tribromide single crystals: gamma spectroscopy applications (#439)

O. Baussens1, G. Montemont1, J. - M. Verilhac2, L. Hirsch3, E. Gros-Daillon1

1 University Grenoble Alpes, CEA, LETI, F38000, Grenoble, France
2 University Grenoble Alpes, CEA, LITEN, F38000, Grenoble, France
3 University of Bordeaux, IMS – CNRS, UMR 5218, Bordeaux INP, ENSCBP, F33405,, Talence, France


Metal halide perovskites have been studied since 2016 for gamma spectroscopy applications. In this work, we study devices based on methylammonium lead tribromide single crystals as gamma detectors. These detectors can measure the signal of a single gamma photon and the energy resolution is mainly limited by the noise of the detectors. We therefore investigated the noise power spectral density of our devices at different bias. At zero polarization voltage, we found that our devices behave as their ideal equivalent electrical circuit. The main noise source is thermal noise. At non-zero polarization voltages, we show that the noise is dominated by the 1/f noise of our devices. Further research will focus on the comprehension of the physical phenomena responsible for the 1/f noise in our devices.

Keywords: Lead halide perovskite, noise power spectral density
10:45 AM R-08-07

Impact of growth pressure on the neutron-detection efficiency of BGaN diodes (#189)

A. Miyazawa1, Y. Ohta1, S. Matsukawa1, K. Hayashi1, H. Nakagawa2, S. Kawasaki3, Y. Ando3, G. Wakabayshi4, Y. Honda5, H. Amano5, 6, K. Shima7, K. Kojima7, S. F. Chichibu5, 7, Y. Inoue1, T. Aoki2, T. Nakano1, 2

1 Shizuoka Univ., Hamamatsu, Japan
2 R. I. E. Shizuoka Univ., Hamamatsu, Japan
3 Nagoya Univ., Nagoya, Japan
4 Atomic Energy Research Institute Kindai Univ., Higashiosaka, Japan
5 IMaSS, Nagoya Univ., Nagoya, Japan
6 Akasaki Research Center, Nagoya, Japan
7 IMRAM, Tohoku Univ., Sendai, Japan


 Neutron-detection using BGaN semiconductor is a novel technology expected to allow the development of neutron-imaging sensors. In previous studies, the suppression of gas phase reaction for the B metal organic source is achieved by metal organic vapor phase epitaxy (MOVPE) using trimethylboron (TMB) which is a new B metal organic source. In this study, the impact of growth pressure on the BGaN crystallinity and detection characteristics was investigated.  
 From the BGaN structural characteristics, in a low growth pressure region (6.7~10 kPa), the degradation of crystallinity was confirmed by the formation of voids due to the desorption of surface adsorption atoms. The BGaN films grown at a growth pressure between 13.3 and 30 kPa were films with flat surface and no void formation, while the film grown at 26.7 kPa had the best surface flatness. At a growth pressure over 40 kPa, the degradation of crystallinity and surface flatness by the gas phase reaction were confirmed.
 Furthermore, PIN diodes were fabricated using BGaN film obtained at each growth pressure, and the neutron-detection characteristics were investigated. The neutron-detection efficiency tends to decrease by increasing the growth pressure. From this tendency, we confirmed that B composition is decreasing by increasing the growth pressure and that there is a greater impact on the neutron-detection efficiency due to the B composition than due to the crystallinity. These results indicate that high neutron-detection efficiency and high quality BGaN detector can be fabricated by epitaxial growth with high B composition at optimized growth pressure.


This work was partly supported by Iketani Science and Technology Foundation, the Cooperative Research Program of “Network Joint Research Center for Materials and Devices”, the joint usage / research program of the Institute of Materials and Systems for Sustainability(IMaSS), Nagoya University and JSPS KAKENHI Grants No. 16H03899 and 19H04394 from MEXT.

Keywords: Neutron detector, BGaN
10:59 AM R-08-08

Cadmium Magnesium Telluride for Next Generation X-Ray Free Electron Laser, Synchrotron and Many Other Applications (#1041)

H. Chen1, S. Trivedi1, R. Sobolewski2

1 Brimrose Technology Corp, Sparks, Maryland, United States of America
2 University of Rochester, Rochester, New York, United States of America


We developed a picosecond photodetector based on our Bridgman grown and specially engineered Cadmium Magnesium Telluride (Cd1-xMgxTe) single crystal that is sensitive to both optical and x-ray pulses for coarse timing in Free Electron Laser applications. Cd1-xMgxTe is a wide bandgap semiconductor material with potential applications, not only in optoelectronics, but also in particle physics as an intense pulse radiation detector for bremsstrahlung, X-ray/gamma ray radiation, thermal neutrons, and medical imaging. However, for femtosecond optical and x-ray cross correlation, the material has to have very short lifetime, a condition that is opposite to that required for nuclear spectroscopy application. At the same time, the material also needs to have very low bulk league current, in the 10th pA range. Hence the ability to tailor or engineer the material is very crucial. In this paper, femtosecond response and the crystal growth of this special engineered cadmium magnesium telluride material will be presented. Other material characterization and transient measurement will also be discussed along with room temperature semiconductor detector performance for other nuclear radiation detection applications.

AcknowledgmentWe gratefully acknowledge the support to this work thru DOE Phase I Program (Award DE-SC0021468), being monitored by Dr. Eliane S. Lessner , PM, ADRP.    
Keywords: Free Electron Laser, Synchrotron, femtosecond optical and x-ray cross correlation, Cadmium Magnesium Telluride, picosecond photodetector

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