Article
Engineering, Electrical & Electronic
K. Majkowycz, K. Murawski, T. Manyk, J. Rutkowski, M. Kopytko, P. Martyniuk
Summary: DLTS measurements were conducted on an HgCdTe heterostructure photodiode grown by MOCVD on a GaAs substrate. Three consecutive etchings were performed to extract defects from different layers of the heterostructure. The experiments revealed the presence of six localized defects in the entire photodiode, two localized defects in the p/T/P+/n+ structure, and five defect levels in the N+/T/p type detector. A deep-trap level at 183 meV above the valence band and a defect level at 0.5Eg indicated the presence of certain mechanisms affecting the dark currents.
JOURNAL OF ELECTRONIC MATERIALS
(2023)
Article
Engineering, Electrical & Electronic
K. Murawski, K. Murawski, T. Manyk, J. Rutkowski, M. Kopytko, P. Martyniuk
Summary: DLTS measurements were performed on HgCdTe photodiode grown by MOCVD, and various localized defects were extracted through different experiments. A deep-trap level and the dominant mechanism of dark current were identified.
JOURNAL OF ELECTRONIC MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Weitao Lian, Rui Cao, Gang Li, Huiling Cai, Zhiyuan Cai, Rongfeng Tang, Changfei Zhu, Shangfeng Yang, Tao Chen
Summary: This study demonstrates the sensitivity of deep-level defects in antimony triselenide to stoichiometry. Amphoteric Sb-Se defects play a critical role in charge recombination and device performance.
Article
Materials Science, Multidisciplinary
Katarzyna Gwozdz, Vladimir Kolkovsky
Summary: In this study, the electrical and structural properties of Ag and AgH-related defects in n- and p-type Si were reinvestigated using DLTS and high-resolution Laplace DLTS. It was found that several AgH-related peaks were observed in hydrogenated Si, which had not been previously reported. The electrical properties of these defects were determined and discussed in detail. The depth profiles of AgH-related defects previously assigned to AgSH and AgSH2 were analyzed using high-resolution Laplace DLTS, and their assignments were questioned.
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
(2021)
Article
Energy & Fuels
Yun Jia, Xiaolei Ding, Rui Wang, Youyang Wang, Shiqi Zheng, Xiaobo Hu, Guoen Weng, Shaoqiang Chen, Takeaki Sakurai, Hidefumi Akiyama
Summary: This article presents a new, widely-used DLTS test and measurement system based on a lock-in amplifier, which efficiently digitizes and analyzes data. The experimental results demonstrate that the performance of this system is consistent with mainstream systems in various test scenarios.
Article
Physics, Multidisciplinary
Tianyu Xie, Zhiyuan Zhao, Maosen Guo, Mengqi Wang, Fazhan Shi, Jiangfeng Du
Summary: Research shows that even under ambient conditions, negatively charged nitrogen-vacancy (NV-) centers in diamond exhibit identical properties at Hz-precision level, offering a method for precision measurements in solids and implying a potential application of an atomiclike clock based on ensemble NV centers.
PHYSICAL REVIEW LETTERS
(2021)
Article
Engineering, Electrical & Electronic
Maddaka Reddeppa, Byung-Guon Park, Kedhareswara Sairam Pasupuleti, Dong-Jin Nam, Song-Gang Kim, Jae-Eung Oh, Moon-Deock Kim
Summary: Understanding the metal/semiconductor interface is crucial for optoelectronic applications, where the study showcases the enhanced electrical transport properties of hydrogen-passivated GaN nanorod-based Schottky diodes. The hydrogenation leads to higher Schottky barrier height and improved photoresponse, attributed to deep defect passivation and surface-state-free interface.
SEMICONDUCTOR SCIENCE AND TECHNOLOGY
(2021)
Article
Engineering, Electrical & Electronic
J. Plesiewicz, P. Kruszewski, V. P. Markevich, P. Prystawko, S. Bulka, M. Hallsal, I. Crowe, L. Sun, A. R. Peaker
Summary: The results of junction spectroscopy measurements on deep-level defects in MOVPE n-GaN samples subjected to 1.5 MeV electron irradiation are compared with published results for epi-GaN materials grown by other techniques. Two new electron traps, EE1 and EE2, are introduced by 1.5-MeV electron irradiation, with electronic levels at about 0.14 and 0.98 eV below the conduction band edge. The EE1 trap exhibits a strong electric field dependence and its activation energy can be lowered by a strong electric field. The complexity of the EE1 trap level structure is revealed through DLTS measurements.
MICROELECTRONIC ENGINEERING
(2023)
Article
Engineering, Electrical & Electronic
Sandeep K. Chaudhuri, Ritwik Nag, Iftikhar Ahmad, Krishna C. Mandal
Summary: Heteroepitaxial metal-oxide-semiconductor (MOS) structures are demonstrated for the first time as radiation detectors for harsh environment applications. The Ni/beta-Ga2O3/4H-SiC MOS structure shows excellent rectification and radiation response.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Engineering, Electrical & Electronic
I. Jabbari, M. Baira, H. Maaref, R. Mghaieth
Summary: This study investigated the characteristics of AlGaN/GaN HEMT transistors at cryogenic temperatures, identifying an electron trap causing a negative shift in the pinch-off voltage and a significant gate leakage current. The E2 deep level is likely related to nitrogen anti-sites generated near the AlGaN/GaN interface during NH3-MOCVD growth.
MICROELECTRONICS RELIABILITY
(2021)
Article
Engineering, Electrical & Electronic
Yixu Yao, Sen Huang, Qimeng Jiang, Xinhua Wang, Lan Bi, Wen Shi, Fuqiang Guo, Tiantian Luan, Jie Fan, Haibo Yin, Ke Wei, Yingkui Zheng, Jingyuan Shi, Yankui Li, Qian Sun, Xinyu Liu
Summary: A drain-controlled current-mode deep level transient spectroscopy (I-DLTS) was developed to investigate the Semi-ON-state current collapse in AlGaN/GaN high electron mobility transistors (HEMTs). By inserting a graded AlGaN back-barrier, the charging of buffer traps induced by hot-electron effect was effectively blocked, resulting in a suppressed current collapse in AlGaN/GaN HEMTs under Semi-ON-state stress.
IEEE ELECTRON DEVICE LETTERS
(2022)
Article
Chemistry, Multidisciplinary
Il-Ho Ahn, Dong Jin Lee, Deuk Young Kim
Summary: This study proposes and demonstrates the use of temperature-dependent curve-fitting error values of the Schottky diode I-V curve as an auxiliary diagnostic signal. The integration of this signal with temperature-scan Capacitance DLTS (CDLTS) signals improves the efficiency and accuracy of Laplace Transform (LT)-DLTS or Isothermal Capacitance transient spectroscopy (ICTS) methods.
Article
Engineering, Electrical & Electronic
Zhengpeng Wang, Hehe Gong, Chenxu Meng, Xinxin Yu, Xinyu Sun, Chongde Zhang, Xiaoli Ji, Fangfang Ren, Shulin Gu, Youdou Zheng, Rong Zhang, Jiandong Ye
Summary: Defects/traps in beta-Ga2O3 have been investigated and identified in Ni/beta-Ga2O3 Schottky barrier diode (SBD) and NiO/beta-Ga2O3 p(+)-n heterojunction diode (HJD) by deep level transient spectroscopy (DLTS). The study provides insights into the carrier transport mechanisms in Ga2O3-based power devices.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2022)
Article
Engineering, Mechanical
S. Fahad, M. Noman, A. F. Qureshi, M. Ali, S. Ahmed
Summary: Photovoltaic solar cells based on thin-film cadmium telluride (CdTe) have shown potential to outperform multi-crystalline silicon solar cells in terms of efficiency, with a record efficiency of 22% reported in literature. However, limitations in achieving the theoretical efficiency of up to 25% are attributed to high recombination trap centers within the CdTe energy band gap. Experimental investigations reveal the presence of these trap centers at specific energy levels, hindering the attainment of the theoretical limits of open circuit voltage.
ENGINEERING FAILURE ANALYSIS
(2021)
Article
Nanoscience & Nanotechnology
Dan Zhang, Zhuogeng Lin, Wei Zheng, Feng Huang
Summary: A back-to-back heterojunction was proposed to fabricate Si-based photovoltaic photodetectors with high deep ultraviolet (DUV) spectral selectivity. The Pt/ZnGa2O4/p-Si DUV photovoltaic detector exhibited a low dark current density, a large photo-to-dark current ratio, and a fast response speed. The performance enhancement was attributed to the higher Schottky barrier established between Pt and ZnGa2O4 in the back-to-back heterojunction structure.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Physics, Condensed Matter
Mylene Sauty, Natalia Alyabyeva, Cheyenne Lynsky, Yi Chao Chow, Shuji Nakamura, James S. Speck, Yves Lassailly, Alistair C. H. Rowe, Claude Weisbuch, Jacques Peretti
Summary: In this study, scanning tunneling electroluminescence microscopy was used to investigate the unique radiative recombination properties near a defect in an InGaN/GaN quantum well. The results revealed intense emission peaks at higher energies close to the defect edges, which were not visible in the macrophotoluminescence spectrum. The quantitative information obtained from fitting the local tunneling electroluminescence spectra provided important insights into carrier localization in the quantum well.
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS
(2023)
Article
Engineering, Electrical & Electronic
R. M. Cadena, D. R. Ball, E. X. Zhang, S. Islam, A. Senarath, M. W. McCurdy, E. Farzana, J. S. Speck, N. Karom, A. O'Hara, B. R. Tuttle, S. T. Pantelides, A. F. Witulski, K. F. Galloway, M. L. Alles, R. A. Reed, D. M. Fleetwood, R. D. Schrimpf
Summary: Low-energy ion-induced breakdown and single event burnout (SEB) were observed in beta-gallium oxide (beta-Ga2O3) Schottky diodes at voltages lower than expected. Different responses were observed for alpha particles, Cf-252, and heavy-ion irradiation. TCAD simulations explained the breakdown as a result of ion strikes and defect-driven breakdown due to displacement-damage-induced defects in beta-Ga2O3. First-principles calculations showed the formation of less resistive defect clusters that can lead to destruction at reduced voltages.
IEEE TRANSACTIONS ON NUCLEAR SCIENCE
(2023)
Article
Physics, Applied
Feng Wu, Jacob Ewing, Cheyenne Lynsky, Michael Iza, Shuji Nakamura, Steven P. DenBaars, James S. Speck
Summary: In this article, the authors used advanced characterization techniques to study the active region compositions, V-defect formation, and V-defect structure in green and red LEDs. They identified two types of V-defects, one that promotes hole injection and one that is believed to be deleterious to high-efficiency LEDs.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Optics
Panpan Li, Hongjian Li, Yifan Yao, Kai Shek Qwah, Mike Iza, James S. Speck, Shuji Nakamura, Steven P. Denbaars
Summary: In this work, we demonstrate the vertical integration of nitride-based blue/green micro-light-emitting diode (mu LED) stacks with independent junction control using a hybrid tunnel junction (TJ). The hybrid TJ was grown by metal-organic chemical vapor deposition (p + GaN) and molecular-beam epitaxy (n + GaN). Different junction diodes were able to generate uniform blue, green, and blue/green emissions. The peak external quantum efficiency (EQE) of the TJ blue mu LEDs and green mu LEDs with indium tin oxide contact were 30% and 12%, respectively. Carrier transportation between different junction diodes was discussed. This work suggests a promising approach for vertical mu LED integration to enhance the output power of single LED chips and monolithic mu LEDs with different emission colors and independent junction control.
Article
Engineering, Electrical & Electronic
M. Ikram Md Taib, M. A. Ahmad, E. A. Alias, A. Alhassan, I. A. Ajia, M. M. Muhammed, I. S. Roqan, S. P. DenBaars, J. S. Speck, S. Nakamura, N. Zainal
Summary: In-surfactant was introduced during the growth of high temperature GaN quantum barriers and GaN interlayer in InGaN/GaN green LEDs. Results showed that the introduction of In-surfactant improved LED growth, particularly in the GaN interlayer. It improved the morphology of the interlayer, allowed it to serve as a good surface growth, and effectively improved the multi-quantum wells. Moreover, the introduction of In-surfactant shifted the emission wavelength towards red, reduced the forward voltage of the LEDs, and allowed faster carrier decay lifetime.
SEMICONDUCTOR SCIENCE AND TECHNOLOGY
(2023)
Article
Nanoscience & Nanotechnology
Matthew S. Wong, Aditya Raj, Hsun-Ming Chang, Vincent Rienzi, Feng Wu, Jacob J. Ewing, Emily S. Trageser, Stephen Gee, Nathan C. Palmquist, Philip Chan, Ji Hun Kang, James S. Speck, Umesh K. Mishra, Shuji Nakamura, Steven P. DenBaars
Summary: The electrical performance of III-nitride blue micro-light-emitting diodes (mu LEDs) with different tunnel junction (TJ) architectures grown by metalorganic chemical vapor deposition is investigated. The introduction of AlGaN layer above the n-side of the TJ layer improves the current density-voltage characteristic and the effects of AlGaN/GaN superlattices are examined. The band diagram simulation shows that a net positive polarization charge is formed at the AlGaN/GaN interface, leading to a reduction in tunneling distance and an increase in tunneling probability. Additionally, the proposed AlGaN-enhanced TJ design significantly enhances the wall-plug efficiency of mu LEDs.
Article
Physics, Applied
Panpan Li, Hongjian Li, Yunxuan Yang, Matthew S. Wong, Mike Iza, Michael J. Gordon, James S. Speck, Shuji Nakamura, Steven P. DenBaars
Summary: This article presents high-performance 10 x 10 μm InGaN amber micro-size LEDs. At 15 A cm(-2), the InGaN micro LEDs exhibit a single emission peak at 601 nm. The peak external quantum efficiency (EQE) and wall-plug efficiency are 5.5% and 3.2%, respectively. Compared to the 100 x 100 μm InGaN red micro LEDs, the 10 x 10 μm InGaN red micro LEDs maintain a similar EQE value with the same efficiency droop. These results highlight the higher efficiency potential of InGaN materials compared to common AlInGaP materials for the ultra-small size red micro LEDs required by augmented reality and virtual reality displays.
APPLIED PHYSICS EXPRESS
(2023)
Article
Optics
J. Mickevic, E. Valkiunaite, Z. Podlipskas, K. Nomeika, S. Nargelas, G. Tamulaitis, Y. C. Chow, S. Nakamura, J. S. Speck, C. Weisbuch, R. Aleksieju
Summary: The dynamics of two distinct bands in non-polar m-plane InGaN/GaN multiple quantum wells (MQWs) were investigated using PL, CL, and DT spectroscopy. The shift in peak emission wavelength with increasing excitation was caused by competition between these bands. DT measurements attributed the high-energy PL band to optical transitions between ground QW states, while the low-energy PL band was associated with recombination of localized carriers. CL measurements confirmed the dispersion of deep localized states and suggested small-scale disorder. PL measurements showed that localized states are highly sensitive to indium content and structural parameters. Temperature-dependent PL studies revealed strong carrier-phonon interaction.
JOURNAL OF LUMINESCENCE
(2023)
Article
Nanoscience & Nanotechnology
Panpan Li, Hongjian Li, Yifan Yao, Norleakvisoth Lim, Matthew Wong, Mike Iza, Michael J. Gordon, James S. Speck, Shuji Nakamura, Steven P. DenBaars
Summary: We have shown a significant improvement in the quantum efficiency of InGaN red micro-light-emitting diodes (mu LEDs). The peak external quantum efficiency (EQE) of the packaged 80 x 80 mu m(2) InGaN red mu LEDs increased to 6.0% at 12A/cm(2), indicating a significant advancement in the efficiency exploration of InGaN red mu LEDs. The enhancement in EQE is attributed to improved quantum efficiency, confirmed by electron-hole wavefunction overlap and photoluminescence intensity ratio analysis. Additionally, ultrasmall 5x 5 mu m(2) InGaN red mu LEDs were obtained with a high peak EQE of 4.5%.
Article
Nanoscience & Nanotechnology
Takeki Itoh, Akhil Mauze, Yuewei Zhang, James S. Speck
Summary: Continuous Si doping in beta-Ga2O3 epitaxial films was achieved using plasma-assisted molecular beam epitaxy with a valved effusion cell for the Si source. Secondary ion mass spectroscopy results indicated flat and sharply turned Si doping profiles in beta-Ga2O3. The Si doping concentration could be controlled by adjusting the cell temperature or the valve aperture of the Si effusion cell. High crystal quality and smooth surface morphologies were observed in Si-doped beta-Ga2O3 films grown on (010) and (001) substrates. The Si-doped (001) beta-Ga2O3 epitaxial film exhibited an electron mobility of 67 cm(2)/Vs at a Hall concentration of 3 x 10(18) cm(-3).
Article
Psychology, Developmental
Erin P. Vaughan, Julianne S. Speck, Paul J. Frick, Toni M. Walker, Emily L. Robertson, James V. Ray, Tina D. Wall Myers, Laura C. Thornton, Laurence Steinberg, Elizabeth Cauffman
Summary: Research on proactive and reactive aggression in adolescents and young adults found that these two types of aggression have unique developmental trajectories and distinct covariates. Proactive aggression was influenced by callous-unemotional traits, while reactive aggression was predicted by impulsivity. These findings highlight the importance of considering the specific factors associated with each type of aggression in understanding and addressing aggressive behaviors.
DEVELOPMENT AND PSYCHOPATHOLOGY
(2023)
Article
Physics, Applied
Wan Ying Ho, Cameron W. Johnson, Tanay Tak, Mylene Sauty, Yi Chao Chow, Shuji Nakamura, Andreas Schmid, Jacques Peretti, Claude Weisbuch, James S. Speck
Summary: In this study, the lateral distribution of the junction current in an electrical biased p-n GaN diode was measured using electron emission microscopy with a low-energy electron microscope. The vacuum level on the diode surface was reduced by cesium deposition to achieve negative electron affinity, allowing emitted overflow electrons on the biased diode surface to be imaged for their spatial distribution. The obtained results were compared with Joyce and Wemple's analytical solutions [J. Appl. Phys. 41, 3818 (1970)] and showed a good match.
APPLIED PHYSICS LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Wan Ying Ho, Abdullah I. Alhassan, Cheyenne Lynsky, Yi Chao Chow, Daniel J. Myers, Steven P. DenBaars, Shuji Nakamura, Jacques Peretti, Claude Weisbuch, James S. Speck
Summary: Using electron emission spectroscopy, researchers measured and analyzed the energy distribution of vacuum emitted electrons from electrically driven InGaN/GaN green light emitting diodes (LEDs) with and without a prewell superlattice (SL). They discovered a high-energy upper valley peak at approximately 1.7 eV above the I' valley in samples without a prewell SL, which is attributed to trap-assisted Auger recombination (TAAR). The absence of this peak in the sample with a prewell SL suggests the gettering of unidentified impurities that act as TAAR centers.
Article
Physics, Applied
Saulius Marcinkevicius, Jacob Ewing, Rinat Yapparov, Feng Wu, Shuji Nakamura, James S. Speck
Summary: Hole injection through V-defect sidewalls into all quantum wells can increase the efficiency of long wavelength GaN light emitting diodes, allowing for population of all wells in a multiple QW structure.
APPLIED PHYSICS LETTERS
(2023)
