Progress in CdZnTe substrate producibility and critical drivers of IRFPA yield originating with CdZnTe substrates

With the goal of maximizing the yield of infrared focal plane arrays (IRFPAs), Santa Barbara Research Center’s (SBRC) Infrared Materials Producibility Program (IRMP) has focused on assessing and improving the quality, yield, and throughput of CdZnTe substrates. A baseline detector lot was fabricated to identify the critical drivers of IRFPA yield coming from the substrates and to evaluate the quality and yield of the current vendor base for CdZnTe substrates. Substrate induced defects and impurities that can potentially affect device performance and operability were carefully mapped out in detail on 44 × 67 mm² size substrates, received from IRMP substrate vendors as well as SBRC. This paper will report on the correlations found between this substrate characterization data base and the IRFPA level defect distributions. Key results from these correlation studies are: (1) extended defects found on the substrates with the Nakagawa etch correlated well with responsivity reduction in the final IRFPA; (2) cross-hatch patterns that were evident in the responsivity map correlated well with similar features seen by x-ray topography on LPE double layers; and (3) a possible correlation of device performance (leakage current at 78K) with copper and lithium impurities in the substrate. Recent initiatives toward improving the quality and yield of the substrate growth process have focused on improving purity in the pre-growth charge preparation, modification of growth parameters to reduce defects and scaling up of the vertical Bridgman growth process from its current 67 mm diameter boule size to 92 mm diameter boules. Promising initial results from the large diameter boule growth process will be shown. The 92 mm diameter CdZnTe boule (6 kg charge) shows two predominant single crystal grains encompassing 75% of boule volume. Defect characterization of boules grown under baseline and modified conditions is discussed.     

Microstructure of epitaxial layers deposited on silicon by ion assisted deposition

We demonstrate the epitaxial growth of silicon with ion assisted deposition on pyramidally structured porous silicon and investigate the microstructure of the epitaxial layer with transmission electron microscopy. The major defects in the grown pyramid structure are stacking faults on the {1 1 1} facets of the pyramids, whereas the epitaxial layers on the {0 0 1} facets are defect-free. The stacking fault density decreases by about three orders with increasing the deposition temperature from 600 to 850°C, but is constant when the ion energy changes. Depending on growth conditions Si-interstitials are built into the layers, which during electron microscopy form so called rod-like defects.     

A new perspective on the characterization of materials for a-Si:H solar cells

A study has been carried out on a-Si:H solar cell materials fabricated under a wide range of deposition conditions in different laboratories. The results on both thin films and corresponding Schottky barrier cell structures demonstrate that analysis and characterization based solely on the neutral dangling bonds are clearly inadequate. Contributions of charged defects to the properties of a-Si:H, their effect on light-induced changes are identified together with the limitations of methods commonly used to characterize the solar cell properties and stability of a-Si:H materials. Self-consistent fitting of a wide range of results on films and Schottky barrier cell structures is obtained with a gap state distribution in which charged defects are included.     

装药缺陷对固体火箭发动机内弹道性能的影响

采用仿真计算分析方法研究了管状推进剂装药缺陷的宽度、深度以及包覆层脱粘等因素对固体火箭发动机内弹道性能的影响规律。结果表明,随着固体推进剂装药裂纹深度与宽度比的增加,燃烧室内压强和裂纹出口气流速度也增加。管状药柱包覆层前端轴向脱粘可使燃面-肉厚曲线的斜率增加,装药的压强指数增大,最终可能造成燃烧室压力过高而解体爆炸。     

激光晶体Nd:YVO4的形貌及生长缺陷

本文报道了应用环境扫描电镜（ESEM）和同步辐射X射线白光形貌术对采用提拉法生长出的Nd:YVO4晶体进行的形貌及生长缺陷的分析,获得了该晶体的开裂表面的ESEM形貌像以及取自晶体肩部和中间部位的（001）面的同步辐射白光形貌像,观察到了位错、包裹物等缺陷,可为生长高质量的Nd:YVO4晶体提供重要的启示.     

Thermodynamic modeling of native point defects and dopants of GaN semiconductors

A thermodynamic modeling of GaN was carried out to describe the thermodynamic behavior of native defects, dopants, and carriers (free electrons and holes) in GaN semiconductors. The compound energy model (CEM) was used. An unintentionally doped GaN was taken as an example. Oxygen was introduced into the model as the unintentionally doped impurity, according to the practical experimental phenomena. The energies of component compounds in the model were defined based on the results of the ab initio calculations and adjusted to fit experimental data. The thermodynamic properties of the defects and the oxygen doped were calculated to show the facility of the model.     

快速预热处理对大直径CZ-Si中FPDs及清洁区的影响

研究了不同气氛下快速预热处理(RTA)后,硅片中的流动图形缺陷(FPDs)密度和随后两步热处理形成的魔幻清洁区(MDZ)之间的关系.硅片经过高温快速预热处理后,再经过800℃(4h)+1000℃(16h)常规退火,以形成MDZ.研究发现,当硅片在Ar气氛或N2/O2(9%)混合气氛下RTA预处理后,FPDs密度较低,随后热处理出现的氧沉淀诱生缺陷密度较高、清洁区较宽.对于N2/O2混和气氛,随着O2含量的增加,FPDs和氧沉淀诱生缺陷密度变小,纯O2气氛下预处理后硅片中FPDs和氧沉淀诱生缺陷密度最低.因此,可以通过调节N2/O2混合气氛中两种气氛的比例来控制空洞型微缺陷和硅片体内氧沉淀诱生缺陷的密度.     

锑化铟晶片高温加速贮存性能变化研究

锑化铟晶片在存放以及使用过程中的性能稳定性是影响制备的探测器性能的重要因素之一。为了探究锑化铟晶片在长时间放置情况下的性能变化情况,对锑化铟晶片进行高温加速贮存试验,并在试验过程中对晶片几何参数、表面粗糙度、电学参数、位错缺陷等几个重要性能参数进行跟踪检测。结果表明,在高温加速试验条件下,除晶片外形发生轻微变化以外,其他性能基本不发生变化,晶片能够长期保存。     

Probing Defects and Spin-Phonon Coupling in CrSBr via Resonant Raman Scattering

Understanding the stability limitations and defect formation mechanisms in 2D magnets is essential for their utilization in spintronic and memory technologies. Here, defects in mono- to multilayer CrSBr are correlated with structural, vibrational, and magnetic properties. Resonant Raman scattering is used to reveal distinct vibrational defect signatures. In pristine CrSBr, it is shown that bromine atoms mediate vibrational interlayer coupling, allowing for distinguishing between surface and bulk defect modes. Environmental exposure is shown to cause drastic degradation in monolayers, with the formation of intralayer defects. This is in contrast to multilayers that predominantly show bromine surface defects. Through deliberate ion irradiation, the formation of defect modes is tuned: these are strongly polarized and resonantly enhanced, reflecting the quasi--1D electronic character of CrSBr. Strikingly, pronounced signatures of spin-phonon coupling of the intrinsic phonon modes and the ion beam-induced defect modes are observed throughout the magnetic transition temperature. Overall, defect engineering of magnetic properties is possible, with resonant Raman spectroscopy serving as a direct fingerprint of magnetic phases and defects in CrSBr.