Negative luminescence in semiconductors: a retrospective view

Twenty-five years ago, we introduced the phenomenon of negative luminescence (NL) into semiconductor physics. This paper provides an overview of work conducted to develop this fundamental concept. Initially, we consider the first-principle approach to radiation interaction with basic matter and the major properties of NL. Then we describe the problems of NL direct measurements in homogeneous materials and structures. Finally, we emphasize the use of NL approach in applications involving devices for infrared (IR) wavelength (3–12 μm) high-temperature (300–400 K) optoelectronics. Our subjects will include NL IR emitting diodes, radiative coolers, IR dynamic scene simulators, light up-conversion devices, and the Stealth effect in IR.     

Analysis and Optimization of Noise in Bipolar RF Harmonic Mixers

A noise analysis of bipolar harmonic mixers (BHM) used for direct-conversion receivers is presented in this paper. Analytical and simulated results for the transfer function of the mixer are presented. Simple analytical expressions describing noise contribution from all sources are derived. Estimation of flicker noise quite agrees with harmonic-balance simulation results. Based on the derived expressions, total time average noise power spectral density (PSD) at the output is compared with simulation results. For the recommended regions of operation, error is less than 20%. The overall BHM noise figure (NF) is calculated and optimized based on a simple extracted formula. Errors introduced by analysis remain within a 1.5-dB margin with respect to simulation results. The validity of analysis for high frequencies is justified. The effect of flicker noise coefficient on the overall mixer NF is compared for different available processes.     

稀土氟化物Y0.97Er0.03F3纳米材料的制备及上转换发光

通过燃烧法和控温热反应法制备了稀土氟化物纳米材料，利用XRD和TEM对样品进行了分析和表征。测量了发射波长为980nm激光二极管激发下所得纳米材料的上转换发光性质。     

Monolithic SiGe Up‐/Down‐Conversion Mixers with Active Baluns

The purpose of this paper is to describe the implementation of monolithically matching circuits, interface circuits, and RF core circuits to the same substrate. We designed and fabricated on‐chip 1 to 6 GHz up‐conversion and 1 to 8 GHz down‐conversion mixers using a 0.8 µm SiGe hetero‐junction bipolar transistor (HBT) process technology. To fabricate a SiGe HBT, we used a reduced pressure chemical vapor deposition (RPCVD) system to grow a base epitaxial layer, and we adopted local oxidation of silicon (LOCOS) isolation to separate the device terminals. An up‐conversion mixer was implemented on‐chip using an intermediate frequency (IF) matching circuit, local oscillator (LO)/radio frequency (RF) wideband matching circuits, LO/IF input balun circuits, and an RF output balun circuit. The measured results of the fabricated up‐conversion mixer show a positive power conversion gain from 1 to 6 GHz and a bandwidth of about 4.5 GHz. Also, the down‐conversion mixer was implemented on‐chip using LO/RF wideband matching circuits, LO/RF input balun circuits, and an IF output balun circuit. The measured results of the fabricated down‐conversion mixer show a positive power conversion gain from 1 to 8 GHz and a bandwidth of about 4.5 GHz.     

一种基于像素自适应仲裁的OSD分层混合结构设计

数据混合是OSD分层显示的关键技术之一.本文基于OSD的分层结构及数据组织结构特点,提出一种OSD分层显示的单混合结构,该结构采用基于像素自适应仲裁的策略,按照层优先级次序,对多个OSD图层信号实时地切换显示.FPGA验证结果表明,该结构在满足OSD分层混合显示、实现菜单选择鼠标控制等高级人机对话功能的前提下,其硬件资源开销比多混合结构节省约33%以上,且具有良好的层次可扩展性和操作灵活性.     

Visible Up-Conversion Luminescence in Ho3+: BaTiO3 Nano-Crystals Prepared by Sol Gel Technique

Visible up-conversion emissions at (435, 545, 580, 675 and 690 nm) and (437, 547 575 and 675 nm) have been observed from the sol-gel derived nano-crystalline Ho³⁺: BaTiO₃ powders and thin films respectively, under 808 nm laser diode excitation emissions. Combined with the energy level structure of Ho³⁺ ions and the kinetics of the visible emissions, the up-conversion mechanism has been analyzed and explained. The blue, green and red emissions of both samples has been attributed to the ground state-directed transition from (⁵F₁), (⁵S₂) and (⁵F₅), which are populated through excited state absorption (ESA) for 808 nm excitation. Nano-structure pure barium titanate and doped with different concentrations of Ho³⁺ ions in the from of powder and thin film have been prepared by sol-gel technique, using barium acetate (Ba(Ac)₂), and titanium butoxide (Ti(C₄H₉O)₄), as precursors. The thin films were prepared by sol-gel spin coating method. The as-grown thin films and powders were found to be amorphous, which crystallized to the tetragonal phase after heating at 750°C in air for 30 minutes. The crystallite sizes of the thin film and powder both doped with 4% Ho³⁺ ions was found to be equal to 11 and 16 nm, respectvely.     

Color tuning of up-conversion emission in ytterbium,erbium, aluminum tri-doped zinc oxide crystal by adjusting aluminum concentration

Ytterbium, erbium, aluminum tri-doped zinc oxide crystal was synthesized, which can turn color from red to green up-conversion luminescence through adjusting aluminum content. When the aluminum concentration reached 4?mol%, the color of up-conversion emission first turn from red to green. Meanwhile, the ratio of red to green emission reduced from 25.32 to 0.26, and the coordinates of chromaticity coordinate calculation changes from (0.5749, 0.3378) to (0.2190, 0.7169) with aluminum concentration range from 0 to 4?mol%. The up-conversion emission peaks at 521, 542, and 660?nm of sample originate from the transitions of ²H_11/2 → ⁴I_15/2, ⁴S_3/2 → ⁴I_15/2, and ⁴F_9/2 → ⁴I_15/2 of erbium ions, respectively. X-ray diffraction patterns perform the better crystallization degree with increasing aluminum concentration. The scanning electron microscopy images show the porous and lamellar structures with different aluminum concentrations. A convenient but effective design to obtain ytterbium, erbium, aluminum tri-doped zinc oxide up-conversion luminescence is reported, which can turn color from red to green.     

Design of 60GHz RF Transceiver in CMOS:Challenges and Recent Advances

With more than 40 years Moore scaling, the speed of CMOS transistors is around 100 GHz. Such fact makes it possible to realize mm-wave circuits in CMOS. However, with the target of achieving broadband and power-efficient operation, 60 GHz CMOS RF transceiver faces severe challenges. After reviewing the technology issues, regarding the 60 GHz applications, this paper discusses design challenges both from the system and the building block levels, and also presents some simulated or measured circuits results.