The beneficial effects of a p-type GaInN spacer layer on the efficiency of GaInN/GaN light-emitting diodes

Light-emitting diodes (LEDs) with a Mg-doped p-type Ga_1−xIn_xN (0 ≤ x ≤ 0.07) spacer layer located between an undoped GaN spacer layer and the electron blocking layer are investigated. The LEDs are found to have comparable peak efficiency but less efficiency droop when the crystal quality of the p-type Ga_1−xIn_xN spacer layer is well-controlled by lowering the growth temperature and by using a suitable In composition and Mg doping concentration. All LED samples with the p-type spacer layer show a smaller efficiency droop compared to a reference LED having an undoped GaN spacer. Among the sample sets investigated, an optical power enhancement of 12% at 111 A/cm² is obtained when inserting a 5 nm-thick p-type Ga_0.97In_0.03N spacer layer. The results support that carrier transport is the key factor in the efficiency droop observed in GaN-based LEDs.     

Effects of junction defect healing in Germanium n-MOSFET through thermal annealing

In this paper, the impact of junction defect healing through thermal annealing in Ge n-metal-oxide-semiconductor field-effect transistors (MOSFETs) is thoroughly investigated. Germanium (Ge) is strongly affected by the presence of point defects within the crystal, which is the source of leakage current and low frequency noise. For MOSFET applications, these defects at the junction of the source and drain area are created by ion implantation. However, these can be significantly reduced by proper thermal treatment. Here, the effect of defect healing is investigated and presented through current–voltage characteristics of a n⁺/p diode and MOSFET I_D-V_G measurement, and secondary ion mass spectroscopy (SIMS).     

基于双极性铼配合物的低浓度淬灭电致发光器件

合成了一种含双极性9,9-双(9-乙基咔唑-3-基)-4,5-二氮芴(ECAF)配体的新型三羰基铼配合物Re(CO)3(ECAF)Cl,通过核磁共振氢谱及高分辨质谱对其结构进行了确定。以含有4,5-二氮-9,9-螺二芴(SB)配体的铼配合物Re(CO)3(SB)Cl作为参比物,对比研究了其热稳定性及光电性能。结果表明,与参比物的分解温度(366℃)相比,配合物Re(CO)3(ECAF)Cl有极好的热稳定性(热分解温度419℃)。由于富电子咔唑基团导致的能隙增大,相比参比物的发光波长(572 nm),Re(CO)3(ECAF)Cl的发光波长蓝移至565 nm。Re(CO)3(ECAF)Cl的发光量子效率(39%)稍高于参比物(37%)。以旋涂法制成电致发光器件后,基于Re(CO)3(ECAF)Cl器件的最佳掺杂浓度(质量分数)高达30%,是基于参比物器件的2.4倍,而且开启电压低至2.9 V,明显比参比物器件的4.0 V低,说明ECAF配体能有效抑制发光浓度淬灭,且明显改善了铼配合物的载流子传输性能。基于Re(CO)3(ECAF)Cl器件的最大电流效率及最大外量子效率分别为8.2 cd·A^-1和3.0%,低于参比物器件的9.7 cd·A^-1和3.9%。     

Remote Actuation of a Light-Emitting Device Based on Magnetic Stirring and Wireless Electrochemistry

We propose a straightforward access to a rotating light-emitting device powered by wireless electrochemistry. A magnetic stirrer is used to rotate a light-emitting diode (LED) due to the intrinsic magnetic properties of the tips that contain iron. At the same time, the LED is submitted to an electric field and acts as a bipolar electrode. The electrochemical processes that are coupled on both extremities of the LED drive an electron flow across the device, resulting in light emission. The variation of the LED alignment in time enables an alternating light emission that is directly controlled by the rotation rate. The stirring also enables a continuous mixing of the electrolyte that improves the stability of the output signal. Finally, the LED brightness can readily reveal a change of chemical composition in the electrolyte solution.     

Terahertz radiation generation by beating of two spatial-Gaussian lasers

Terahertz radiation generation is proposed based on beating of two spatial-Gaussian lasers in a periodic density plasma, where a transverse component of current is realized that resonantly excites the radiation with efficiency ∼10⁻³. Importance of laser-beam-width, amplitude and periodicity of density structure is discussed for the efficient THz generation.     

On the energy-dependent number of electronic states in a quantum-well laser diode under a perpendicular magnetic field

The number of electronic states in a quantum-well laser diode under a perpendicular, uniform and time-independent magnetic field is considered as a function of the electronic energy. Within this framework, the energy-averaged number of states is calculated over a suitable energy range. In particular, an expression for the above average number is given when the magnetic field is relatively weak and the devices are assumed to be quasi-one-dimensional.     

Interaction of Short Laser Pulses in Wavelength Range from Infrared to X‐ray with Metals,Semiconductors, and Dielectrics

Laser‐matter interaction is defined by an electronic band structure of condensed matter and frequency ω_L of electromagnetic radiation. In the range of moderate fluences, the energy absorbed by electrons from radiation finally thermalizes in the ion thermal energy. The thermalization processes are different for optical as compared with X‐ray quanta and for metals relative to semiconductors and dielectrics, since the light absorption and electron‐electron, electron‐ion dynamics are sensitive to the electron population in a conduction band and the width of a forbidden gap. Although the thermalization processes are different, the final state is simply a heated matter. Laser heating creates powerful stresses in a target if duration of a laser pulse τ_L is short in acoustic time scale. Nucleation and material removal take place under such stresses. Such way of removal is called here the spallative ablation. Thus the spallative ablation is an ablation mechanism universally important for qualitatively different materials and quanta (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A narrow-linewidth continuous wave Ho：YAL03 laser with Fabry-Perot etalons

A narrow linewidth continuous wave Ho：YAP laser with two Fabry-Perot etalons pumped by a Tm：YLF laser is reported. The maximum output power reaches 8.3 W when the incident pump power is 15.8 W, with 52.5% optical-to- optical conversion efficiency and 62.6% slope efficiency. A stable laser output at 2118.1 nm is achieved, with a linewidth less than 0.4 nm （full width at half maximum）. The beam quality factor is M2- 1.25, measured by the traveling knife-edge method.     

Nonstoichiometric laser materials: Designer wavelengths in neodymium-doped garnets

The tunable nature of lasers provides for a wide range of applications. Most applications rely on finding available laser wavelengths to meet the needs of the research. This article presents the concept of compositional tuning, whereby the laser wavelength is designed by exploiting nonstoichiometry. For research where precise wavelengths are required, such as remote sensing, this is highly advantageous. A theoretical basis for the concept is presented and experimental results in spectroscopic measurements support the theoretical basis. Laser operation nicely demonstrates the validity of the concept of designer lasers.