arXiv subjects

Wenqing Song

Publications and source records attributed to Wenqing Song.

9 recordsLinked to original sources

arXiv2026

Reducing Power Consumption of Embedded Dynamic Memories with ECCs

Gain-cell embedded dynamic random-access memory (GCRAM) offers dense and energy-efficient on-chip storage, but retention-time variations force frequent refresh operations to cover worst-case bits. Error-correction codes (ECCs) can alleviate this limitation by masking bit errors from weak cells and thereby reduce refresh cost. However, the trade-off between the additional access and logic energy introduced by ECCs and the power savings from longer refresh intervals is nontrivial, especially considering the wide range of available ECC options. To optimize overall power consumption, we propose an ECC selection method that combines a refresh-interval model with power analysis to identify the minimum-power ECC configurations under a given yield constraint. Across different memory bandwidths, activity factors, and read/write ratios, the evaluation results show that the best ECC option shifts from stronger codes in refresh-dominated operating regions to lower-overhead codes in access-dominated regions and achieves 46.8% to 94.8% reduction in total power relative to the no-ECC reference.

cs.IT↗

arXiv2026

High-throughput Low-latency Hardware Implementation of BCH Decoders

Two well-known decoding algorithms for BCH codes are conventional decoding, based on the Berlekamp-Massey algorithm in combination with Chien search, and direct decoding, which uses direct solutions to find the error locator polynomial and its roots. We introduce hardware architectures for conventional and direct decoding of extended BCH codes. Both architectures support implementation for any blocklength. Our conventional decoder supports any error-correction capability, whereas direct decoding is supported up to error correcting capability t = 4. To the best of our knowledge, our work is the first to implement a direct BCH decoder with an error-correction capability 4. We synthesize for the Xilinx Ultrascale+ XCZU48DR field-programmable gate-array and 16 nm FinFET for blocklengths up to 1024 bits and t = 4. We show that the direct decoder outperforms the conventional decoder in area efficiency for t = 2, t = 3, and for t = 4 for blocklengths longer than 256. Post-synthesis results for 16 nm FinFET show codeword per clock-cycle throughput at 1 GHz, achieving 239 Gb/s for the (256, 239) eBCH code and 223 Gb/s for (256, 223) eBCH code at 2 ns and 8 ns latency, respectively.

cs.IT↗

arXiv2026

Maximum Coverage Chase Decoder for Optical Interconnects

We propose a low-complexity Chase decoder for optical interconnects that formulates test pattern selection as a generalized maximum coverage problem. For concatenated RS-BCH and oFEC codes, our decoder achieves the standard Chase decoding performance with 25% and 61.3% fewer test patterns, respectively.

cs.IT↗

arXiv2025

Rewritable Complementary Nanoelectronics Enabled by Electron-Beam Programmable Ambipolar Doping

The ability to reversibly and site-selectively tune ambipolar doping in a single semiconductor is crucial for reconfigurable electronics beyond silicon, but remains highly challenging. Here, we present a rewritable architecture based on electron-beam programmable field-effect transistors (FETs). Using WSe$_2$ as a model system, we demonstrate electron-beam-induced doping that enables reversible, precisely controlled carrier modulation exceeding $10^{13}$ cm$^{-2}$. The in-situ writing, erasing, and rewriting of ambipolar doping of nanoscale patterns was directly visualized by scanning microwave impedance microscopy. This mask-free, lithography-compatible approach can achieve precise band engineering within individual channels, yielding near-ideal subthreshold swings (~ 60 mV/dec) and finely tunable threshold voltages for both carrier types without specialized contact engineering. These capabilities allow on-demand realization of high performance logic, including CMOS inverters with high voltage gains and low power consumption, as well as NAND-to-NOR transitions on the same device via direct polarity rewriting. Our platform offers a scalable and versatile route for rapid prototyping of complementary electronics.

cond-mat.mtrl-sci↗

arXiv2025

Acoustoelectric Probing of Fractal Energy Spectra in Graphene/hBN Moir\'e Superlattices

Moir\'e superlattices with long-range periodicity exhibit Hofstadter energy spectra under accessible magnetic fields, enabling the exploration of emergent quantum phenomena through a hierarchy of fractal states. However, higher-order features, located at elevated energies with narrow bandwidths, typically require high carrier densities and remain difficult to resolve using conventional electrical transport due to limited sensitivity and strong background conductivity. Here, we utilize acoustoelectric (AE) transport to probe high-order fractal states and the Hofstadter spectrum in graphene/hBN moir\'e superlattices. Surface acoustic waves on a ferroelectric LiNbO$_3$ substrate generate an AE voltage proportional to the derivative of electrical conductivity, significantly enhancing sensitivity to weak spectral features. Combined with substrate-induced high electron doping, this technique resolves fractal Brown-Zak oscillations up to the fifth-order and provides the first AE observation of the Hofstadter butterfly, revealing high-order fractal magnetic Bloch states and symmetry-broken Landau levels over a wide carrier density range. Our results establish AE transport as a powerful derivative-sensitive probe for emergent fractal quantum states in moir\'e-engineered 2D systems.

cond-mat.mes-hall↗

arXiv2025

Unexpected large electrostatic gating by pyroelectric charge accumulation

Pyroelectricity refers to the accumulation of charges due to changes in the spontaneous polarization of ferroelectric materials when subjected to temperature variations. Typically, these pyroelectric charges are considered unstable and dissipate quickly through interactions with the external environment. Consequently, the pyroelectric effect has been largely overlooked in ferroelectric field-effect transistors. In this work, we leverage the van der Waals interface of hBN to achieve a substantial and long-term electrostatic gating effect in graphene devices via the pyroelectric properties of a ferroelectric LiNbO3 substrate. Upon cooling, the polarization change in LiNbO3 induces high doping concentrations up to 1013 cm-2 in the adjacent graphene. Through a combination of transport measurements and non-contact techniques, we demonstrate that the pyroelectric charge accumulation, as well as its enhancement in electric fields, are responsible for this unexpectedly high doping level. Our findings introduce a novel mechanism for voltage-free electrostatic gating control with long retention.

cond-mat.mtrl-sci↗

arXiv2025

Broadband photoresponse enhancement by band engineering in Sb-doped MnBi2Te4

Topological materials have attracted considerable attention for their potential in broadband and fast photoresponse, particularly in the infrared regime. However, the high carrier concentration in these systems often leads to rapid recombination of photogenerated carriers, limiting the photoresponsivity. Here, we demonstrate that Sb doping in MnBi2Te4 effectively reduces carrier concentration and suppresses electron-hole recombination, thereby significantly improving the optoelectronic performance across the visible to mid-infrared spectra. The optimally doped Mn(Bi0.82Sb0.18)2Te4 photodetector achieves a responsivity of 3.02 mA W-1 with a response time of 18.5 {\mu}s at 1550 nm, and 0.795 mA W-1 with a response time of 9.0 {\mu}s at 4 {\mu}m. These values represent nearly two orders of magnitude improvement compared to undoped MnBi2Te4. Our results highlight band engineering as an effective strategy to enhance the infrared performance of topological material-based photodetectors, opening new avenues for high-sensitivity infrared detection.

cond-mat.mtrl-sci↗

arXiv2024

Edge-Spreading Raptor-Like LDPC Codes for 6G Wireless Systems

Next-generation channel coding has stringent demands on throughput, energy consumption, and error rate performance while maintaining key features of 5G New Radio (NR) standard codes such as rate compatibility, which is a significant challenge. Due to excellent capacity-achieving performance, spatially-coupled low-density parity-check (SC-LDPC) codes are considered a promising candidate for next-generation channel coding. In this paper, we propose an SC-LDPC code family called edge-spreading Raptor-like (ESRL) codes. Unlike other SC-LDPC codes that adopt the structure of existing rate-compatible LDPC block codes before coupling, ESRL codes maximize the possible locations of edge placement and focus on constructing an optimal coupled matrix. Moreover, a new graph representation called the unified graph is introduced. This graph offers a global perspective on ESRL codes and identifies the optimal edge reallocation to optimize the spreading strategy. We conduct comprehensive comparisons of ESRL codes and 5G-NR LDPC codes. Simulation results demonstrate that when all decoding parameters and complexity are the same, ESRL codes have obvious advantages in error rate performance and throughput compared to 5G-NR LDPC codes in some specific scenarios (low and high number of iterations), making them a promising solution towards next-generation channel coding.

cs.IT↗

arXiv2024

Frequency-Modulation Mode-Locked Laser with GHz Spectral Width Tunable in the 2-3 um Region

A narrow-bandwidth actively mode-locked laser using a Cr:ZnS gain medium has been successfully demonstrated. A free-space electro-optic phase modulator is employed in the solid-state laser resonator to achieve frequency-modulation (FM) mode-locking, which achieves a narrow spectral width of ~1 GHz and a pulse duration of ~500 ps over a wide tuning range of 1947-2445 nm. The operation frequency of the modulator determines the repetition rate of the mode-locked pulse train and can stabilize it to millihertz-level without any additional feedback loop systems. We also study the theoretical expression of pulse duration and spectral width in a FM mode-locking in a laser cavity that contains considerable group-delay dispersion. The results indicates that larger intracavity dispersion can only stabilize the laser operation by avoiding mode switching, but also narrow the spectral width and increase the pulse duration. The proposed laser features a narrow spectral width at a desired mid-infrared wavelength and a comb-like spectral structure with stabilized longitudinal mode spacing, providing a powerful tool for sensing and control of molecules.

physics.optics↗