In this work, we have investigated the variation of internal electric field of 4-period In0.16Ga0.84N/pseudo-AlInGaN multiquantum wells (MQWs) embedded in p-i-n structure by surface acoustic waves (SAWs). The pseudo-AlInGaN barriers consist of two In0.16Ga0.84N(11 Å) sandwiched by three Al0.064Ga0.936N (15 Å). The equivalent indium and aluminum compositions in pseudo-AlInGaN barrier are 0.043 and 0.052, respectively, which can be calculated by volume ratio. For reference purpose, In0.16Ga0.84N/GaN MQWs was also used. To generate surface acoustic wave, interdigital patterns with 1 μm finger width were fabricated by e-beam lithography. The piezoelectric fields for GaN barrier and pseudo- Al0.043In0.052Ga0.905N barrier samples are found to be 1.5 MV/cm, 0.33 MV/cm from bias-PL. From μ-PL measurement for pseudo-Al0.043In0.052Ga0.905N barrier sample, we observed lowest luminescence intensity at 100 MHz and 13 dBm in radio frequency (RF) generator, which means that electron-hole recombination can be suppressed by SAWs. The Photocurrent measurement for pseudo-Al0.043In0.052Ga0.905N barrier sample was observed increasing around 2 orders of magnitude at 100 MHz when compare to GaN barrier sample. Based on our results, the reduced piezoelectric field added to SAWs can be provided one of the solutions for enhancing photocurrent in III-nitride photovoltaic devices by extract carriers from quantum wells easily and enhancing traveling length of carriers.
Proc. SPIE. 11201, SPIE Micro + Nano Materials, Devices, and Applications 2019
KEYWORDS: Semiconductors, Thin films, Light emitting diodes, Solid state lighting, Semiconductor materials, Manganese, Field emission displays, Solid state electronics, Thin film devices, Magnetic semiconductors
The novel green luminescent material of the semiconductive nanoporous ZnMnO thin film was fabricated by grain boundary engineering and thermal stress engineering via the thermal nucleation of the sputter-grown ZnMnO layers. Nanoporous ZnMnO exhibited the strong green luminescence characteristics, attributing to the photon confinement at the localized green-emission band formed near the edge area of ZnMnO nanopores. Using semiconductive nanoporous ZnMnO, two different types of high-performance solid-state lighting devices (i.e., field emission device and light-emitting diode) were demonstrated as tangible applications of semiconductive nanoporous ZnMnO.
The combination of a wavelength tunable UV free electron laser and a high resolution photo-electron emission microscope offers unprecedented opportunities for in situ, real time imaging of the dynamics of processes on surfaces on a nanometer scale. This type of system is now in operation at the Duke University Free Electron Laser Laboratory. In this study we report real time observations of the dynamics of liquid Pt-Si islands on Si(100) surfaces. The dynamics of coalescence is observed. Moreover, a driving force for motion of the liquid micro-droplets is developed based on these observations. We also report studies of the dynamics of growth of nanometer scale TiSi2 islands on Si(111). Depending on the growth conditions, we observe ripening or coalescence processes where smaller islands evolve into larger islands. On the (111) surface a shape transition is observed in which the islands are initially circular and then develop into long wire shaped structures. The growth processes represent a competition between kinetic and energetic processes on the surfaces.