Review Articles
  • Silicon-based FMCW signal generators: A review

    Wei Deng, Haikun Jia, Baoyong Chi

    J. Semicond.  2020, 41 (11): 111401

    doi: 10.1088/1674-4926/41/11/111401

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    FMCW radars with high resolution necessities the generation of highly linear, low phase noise, and low spur chirp signals with large bandwidth and a short modulation period. This paper reviews recent research progress on silicon-based FMCW signal generators, identifies advances in architecture, fundamental design, performance analysis, and applications of the FMCW synthesizer.

  • CMOS analog and mixed-signal phase-locked loops: An overview

    Zhao Zhang

    J. Semicond.  2020, 41 (11): 111402

    doi: 10.1088/1674-4926/41/11/111402

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    CMOS analog and mixed-signal phase-locked loops (PLL) are widely used in varies of the system-on-chips (SoC) as the clock generator or frequency synthesizer. This paper presents an overview of the AMS-PLL, including: 1) a brief introduction of the basics of the charge-pump based PLL, which is the most widely used AMS-PLL architecture due to its simplicity and robustness; 2) a summary of the design issues of the basic CPPLL architecture; 3) a systematic introduction of the techniques for the performance enhancement of the CPPLL; 4) a brief overview of ultra-low-jitter AMS-PLL architectures which can achieve lower jitter (< 100 fs) with lower power consumption compared with the CPPLL, including the injection-locked PLL (ILPLL), sub-sampling (SSPLL) and sampling PLL (SPLL); 5) a discussion about the consideration of the AMS-PLL architecture selection, which could help designers meet their performance requirements.

  • Error suppression techniques for energy-efficient high-resolution SAR ADCs

    Jiaxin Liu, Xiyuan Tang, Linxiao Shen, Shaolan Li, Zhelu Li, Wenjuan Guo, Nan Sun

    J. Semicond.  2020, 41 (11): 111403

    doi: 10.1088/1674-4926/41/11/111403

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    The successive approximation register (SAR) is one of the most energy-efficient analog-to-digital converter (ADC) architecture for medium-resolution applications. However, its high energy efficiency quickly diminishes when the target resolution increases. This is because a SAR ADC suffers from several major error source, including the sampling kT/C noise, the comparator noise, and the DAC mismatch. These errors are increasing hard to address in high-resolution SAR ADCs. This paper reviews recent advances on error suppression techniques for SAR ADCs, including the sampling kT/C noise reduction, the noise-shaping (NS) SAR, and the mismatch error shaping (MES). These techniques aim to boost the resolution of SAR ADCs while maintaining their superior energy efficiency.

  • A survey of high-speed high-resolution current steering DACs

    Xing Li, Lei Zhou

    J. Semicond.  2020, 41 (11): 111404

    doi: 10.1088/1674-4926/41/11/111404

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    Digital to analog converters (DAC) play an important role as a bridge connecting the analog world and the digital world. With the rapid development of wireless communication, wideband digital radar, and other emerging technologies, better performing high-speed high-resolution DACs are required. In those applications, signal bandwidth and high-frequency linearity often limited by data converters are the bottleneck of the system. This article reviews the state-of-the-art technologies of high-speed and high-resolution DACs reported in recent years. Comparisons are made between different architectures, circuit implementations and calibration techniques along with the figure of merit (FoM) results.

  • A comparative study of digital low dropout regulators

    Mo Huang, Yan Lu, Rui P. Martins

    J. Semicond.  2020, 41 (11): 111405

    doi: 10.1088/1674-4926/41/11/111405

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    Granular power management in a power-efficient system on a chip (SoC) requires multiple integrated voltage regulators with a small area, process scalability, and low supply voltage. Conventional on-chip analog low-dropout regulators (ALDOs) can hardly meet these requirements, while digital LDOs (DLDOs) are good alternatives. However, the conventional DLDO, with synchronous control, has inherently slow transient response limited by the power-speed trade-off. Meanwhile, it has a poor power supply rejection (PSR), because the fully turned-on power switches in DLDO are vulnerable to power supply ripples. In this comparative study on DLDOs, first, we compare the pros and cons between ALDO and DLDO in general. Then, we summarize the recent DLDO advanced techniques for fast transient response and PSR enhancement. Finally, we discuss the design trends and possible directions of DLDO.

  • A survey of active quasi-circulators

    Bingjun Tang, Li Geng

    J. Semicond.  2020, 41 (11): 111406

    doi: 10.1088/1674-4926/41/11/111406

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    With the development of multi-band wireless communication and the increasing data transmission rate, the circulator as an antenna interface must be able to work in multiple frequency bands and provides large bandwidth. It presents a high challenge to the design of circulators, especially the active quasi-circulators. In this survey, we review the representative active quasi-circulators and summarize three different techniques and the corresponding structures to show an incremental improvement of the isolation and bandwidth of the active quasi-circulators. In addition, we also compare the performance of several state-of-art active circulators, and analyze their advantages and disadvantages. Finally, we conclude the future trend of the active quasi-circulators.

  • Challenges and opportunities toward fully automated analog layout design

    Hao Chen, Mingjie Liu, Xiyuan Tang, Keren Zhu, Nan Sun, David Z. Pan

    J. Semicond.  2020, 41 (11): 111407

    doi: 10.1088/1674-4926/41/11/111407

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    Realizing the layouts of analog/mixed-signal (AMS) integrated circuits (ICs) is a complicated task due to the high design flexibility and sensitive circuit performance. Compared with the advancements of digital IC layout automation, analog IC layout design is still heavily manual, which leads to a more time-consuming and error-prone process. In recent years, significant progress has been made in automated analog layout design with emerging of several open-source frameworks. This paper firstly reviews the existing state-of-the art AMS layout synthesis frameworks with focus on the different approaches and their individual challenges. We then present recent research trends and opportunities in the field. Finally, we summaries the paper with open questions and future directions for fully-automating the analog IC layout.

  • Silicon photonic transceivers for application in data centers

    Haomiao Wang, Hongyu Chai, Zunren Lv, Zhongkai Zhang, Lei Meng, Xiaoguang Yang, Tao Yang

    J. Semicond.  2020, 41 (10): 101301

    doi: 10.1088/1674-4926/41/10/101301

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    Global data traffic is growing rapidly, and the demand for optoelectronic transceivers applied in data centers (DCs) is also increasing correspondingly. In this review, we first briefly introduce the development of optoelectronics transceivers in DCs, as well as the advantages of silicon photonic chips fabricated by complementary metal oxide semiconductor process. We also summarize the research on the main components in silicon photonic transceivers. In particular, quantum dot lasers have shown great potential as light sources for silicon photonic integration—whether to adopt bonding method or monolithic integration—thanks to their unique advantages over the conventional quantum-well counterparts. Some of the solutions for high-speed optical interconnection in DCs are then discussed. Among them, wavelength division multiplexing and four-level pulse-amplitude modulation have been widely studied and applied. At present, the application of coherent optical communication technology has moved from the backbone network, to the metro network, and then to DCs.

  • Optoelectronic and photocatalytic properties of I–III–VI QDs: Bridging between traditional and emerging new QDs

    Yanhong Liu, Fenghua Li, Hui Huang, Baodong Mao, Yang Liu, Zhenhui Kang

    J. Semicond.  2020, 41 (9): 091701

    doi: 10.1088/1674-4926/41/9/091701

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    Due to the quantum size effect and other unique photoelectric properties, quantum dots (QDs) have attracted tremendous interest in nanoscience, leading a lot of milestone works. Meantime, the scope and scientific connotation of QDs are constantly expanding, which demonstrated amazing development vitality. Besides the well-developed Cd-containing II–VI semiconductors, QDs of environmentally friendly I–III–VI (I = Cu, Ag; III = Ga, In; VI = S, Se) chalcogenides have been a hot spot in the QDs family, which are different from traditional II–VI QDs in terms of multi-composition, complex defect structure, synthetic chemistry and optical properties, bringing a series of new laws, new phenomena and new challenges. The composition of I–III–VI chalcogenides and their solid solutions can be adjusted within a very large range while the anion framework remains stable, giving them excellent capability of photoelectric property manipulation. The important features of I–III–VI QDs include wide-range bandgap tuning, large Stokes shift and long photoluminescence (PL) lifetime, which are crucial for biological, optoelectronic and energy applications. This is due to the coexistence of two or more metal cations leading to a large number of intrinsic defects within the crystal lattice also known as deep-donor-acceptor states, besides the commonly observed surface defects in all QDs. However, a profound understanding of their structure and optoelectronic properties remains a huge challenge with many key issues unclear. On one hand, the achievements and experience of traditional QD research are expected to provide vital value for further development of I–III–VI QDs. On the other hand, the understanding of the emerging new QDs, such as carbon and other 2D materials, are even more challenging because of the dramatically different composition and structure from II–VI semiconductors. For this, I–III–VI QDs, as a close relative to II–VI QDs but with much more complex composition and structure variation, provide a great opportunity as a gradual bridge to make up the big gap between traditional QDs and emerging new QDs, such as carbon dots. Here, we hope to compare the research progress of I–III–VI QDs and II–VI QDs, in an effort to comprehensively understand their structure, synthetic chemistry, optical electronic and photocatalytic properties. We further give insights on the key potential issues of I–III–VI QDs from the perspective of bridging between traditional QDs and emerging carbon dots, especially the profound principles behind synthetic chemistry, PL mechanism and optoelectronic applications.

  • Engineering the photoelectrochemical behaviors of ZnO for efficient solar water splitting

    Mengmeng Ma, Yanbin Huang, Jun Liu, Kong Liu, Zhijie Wang, Chao Zhao, Shengchun Qu, Zhanguo Wang

    J. Semicond.  2020, 41 (9): 091702

    doi: 10.1088/1674-4926/41/9/091702

    Abstract Full Text PDF Get Citation

    Solar water splitting is a promising strategy for the sustainable production of renewable hydrogen and solving the world’s crisis of energy and environment. The third-generation direct bandgap semiconductor of zinc oxide (ZnO) with properties of environmental friendliness and high efficiency for various photocatalytic reactions, is a suitable material for photoanodes because of its appropriate band structure, fine surface structure, and high electron mobility. However, practical applications of ZnO are usually limited by its high recombination rate of photogenerated electron–hole pairs, lack of surface reaction force, inadequate visible light response, and intrinsic photocorrosion. Given the lack of review on ZnO’s application in photoelectrochemical (PEC) water splitting, this paper reviews ZnO’s research progress in PEC water splitting. It commences with the basic principle of PEC water splitting and the structure and properties of ZnO. Then, we explicitly describe the related strategies to solve the above problems of ZnO as a photoanode, including morphology control, doping modification, construction of heterostructure, and the piezo-photoelectric enhancement of ZnO. This review aims to comprehensively describe recent findings and developments of ZnO in PEC water splitting and to provide a useful reference for the further application and development of ZnO nanomaterials in highly efficient PEC water splitting.

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