Yerassyl Yerlanuly a b c 1, Hryhorii P. Parkhomenko d 1, Rakhymzhan Ye Zhumadilov a c, Renata R. Nemkayeva a c, Gulnur Akhtanova d, Mykhailo M. Solovan e, Andrii I. Mostovyi d f, Sagi A. Orazbayev a c, Almasbek U. Utegenov a c, Tlekkabul S. Ramazanov a, Maratbek T. Gabdullin a b c, Askhat N. Jumabekov d, Viktor V. Brus d
a Al-Farabi Kazakh National University, Almaty, 050040, Kazakhstan
b Kazakh-British Technical University, Almaty, 050000, Kazakhstan
c Institute of Applied Science and Information Technologies, Almaty, 050038, Kazakhstan
d Department of Physics, Nazarbayev University, Astana, 010000, Kazakhstan
e Faculty of Physics, Adam Mickiewicz University, Poznanv, 61-614, Poland
f Department of Electronics and Energy Engineering, Yuriy Fedkovych Chernivtsi National University, Chernivtsi, 58012, Ukraine
## Abstract
This study proposed self-adaptive nanostructured heterojunction UV-VIS-NIR photodiodes carbon nanowalls (CNWs)/cadmium zinc telluride (CdZnTe) exhibiting stable photoelectric characteristics under ionizing radiation conditions. We carried out a comprehensive analysis of the impact of proton radiation with an energy of 1.5 MeV and a total fluence of 1012 protons/cm2 on the properties of CNWs and CdZnTe functional layers, as well as on the main photodiode characteristics of the CNWs/CdZnTe heterojunctions, employing a set of state-of-the-art materials and device characterization techniques. Responsivity and detectivity of the prepared heterojunctions even slightly improve after exposure to harsh ionizing radiation conditions due to the unique radiation-induced self-adaptive features of the CNWs/CdZnTe heterojunction interface. The characteristics of the CNWs/CdZnTe photodiodes before and after high-energy proton bombardment demonstrate excellent stability, which is the key requirement for long-term and reliable operation of optoelectronic devices in space or radioactively contaminated environments.
## Introduction
The active development of the aerospace industry, nuclear power plants, radiation medicine, and particle physics experiments, where the main processes occur in environments with high levels of ionizing radiation, requires the development of radiation-resistant optoelectronic devices for accurate and reliable measurements, communication, and control systems [[1], [2], [3], [4]]. Photodetectors are widely used optoelectronic devices in modern engineering and information transmission. This category includes various devices such as photoconductors, photodiodes, phototransistors, avalanche photodetectors, and quantum well detectors [5,6]. Conventional narrow or medium bandgap semiconductors, such as Ge, Si, and GaAs, are commonly used in optoelectronic devices. However, these materials possess low resistance to ionizing radiation. High-energy particles interacting with these semiconductors cause displacement defects in the crystalline structure and can lead to device malfunctions [[7], [8], [9], [10]]. Therefore, developing radiation-resistant UV-VIS-NIR photodetectors with stable photoelectric parameters for application in space exploration, nuclear power plants, particle physics experiments, medical imaging, and radiation therapy became an important materials science, device physics, and engineering challenge.
In the last few years, there have been many reports in the literature on hybrid organic-inorganic perovskite-based photodiodes, which have shown promising performance for various applications due to their high responsivity, low noise, and fast response time which are close to that of the commercially available photodiodes [[11], [12], [13], [14]]. Hybrid perovskites demonstrated superior radiation resistance compared to conventional semiconductors such as Ge, Si, GaAs, and CdTe [[15], [16], [17], [18], [19]]. However, the stability of perovskite-based photodetectors is a major concern, especially for long-term operation. The intrinsic chemical instability of hybrid perovskite materials is mainly attributed to their sensitivity to moisture, oxygen, light, and heat, which results in the inevitable degradation of the perovskite active layer, and reduced photodetector performance [[20], [21], [22]]. Given these factors, perovskite-based photodetectors require further research and development.
Cadmium zinc telluride (CdZnTe) is one of the most promising materials for creating radiation-resistant optoelectronic devices. CdZnTe is a p- or n-type semiconductor, depending on its stoichiometric composition, and has a wide bandgap (∼1.46–2.2 eV) determined by the Zn content [23,24]. It is a direct bandgap semiconductor with a large absorption coefficient for efficiently converting optical signals to electrical ones [25]. Furthermore, it is worth noting that CdZnTe has already been widely used in X-ray or gamma-ray radiation detectors, nuclear spectroscopy, and medical imaging that operate under high ionizing radiation conditions [[26], [27], [28], [29], [30]]. Thus, CdZnTe, which has good optoelectronic properties, chemical stability, and radiation resistance, can be successfully used to develop durable UV-VIS-NIR photodetectors. TiN/CdZnTe heterojunction photodiodes have been recently reported to demonstrate outstanding detectivity, response time, and radiation resistance concurrently, surpassing other heterojunction photodiodes and photodetectors that are based on photoactive compound inorganic semiconductor materials [3]. Although TiN/CdZnTe heterojunction photodiodes revealed a significantly higher resistance to ionizing radiation than their Si-based counterparts, their photoelectric characteristics still noticeably deteriorate due to proton-irradiation. This may cause unwanted misfunctioning of optoelectronic circuits over a prolonged operation time. Therefore, the next step is to develop novel chemically stable heterojunction photodiodes with decent photoelectric characteristics which do not deteriorate regardless of harsh ionizing radiation conditions.
Various transparent conductive materials can be used to fabricate CdZnTe-based heterojunction photodiodes [3,31]. Advances in nanotechnology over the past few decades have led to new tools and opportunities in the field of electronics and sensors, which form the basis for the development of nanoelectronics [32]. Nanomaterials possess unique properties that allow for the development and cost-effective production of next-generation electronic and optoelectronic devices that outperform their conventional counterparts [33]. One of the most promising and highly anticipated nanomaterials is Carbon Nanowalls (CNWs) [34,35], which consist of connected flakes or wall-like clusters of graphene sheets standing vertically on a substrate. CNWs are known for their chemical and structural stability and excellent electron mobility. Moreover, in recent years, CNWs have attracted increasing interest in photodetection [[36], [37], [38], [39], [40], [41]]. In addition, our recent work demonstrated the high radiation resistance of CNWs under 5 MeV electron and 1.8 MeV proton irradiation with accumulated fluences of 7 × 1013 e/cm2 and 1012 p/cm2, respectively [36].
This contribution is dedicated to developing stable heterojunction photodiodes with radiation-immune photoelectric characteristics using the lift-off deposition of CNWs ‘window’ functional layer onto CdZnTe single-crystal active layer.
CdZnTe Association (CdZnTe.com)
https://www.cdznte.com/thesis/achieving-stable-photodiode-characteristics-under-ionizing-radiation-with-a-self-adaptive-nanostructured-heterojunction-cnws-cdznte.html