Structure optimization of field-plate AlGaN/GaN HEMTs

AlGaN/GaN high electron mobility transistors (HEMTs) on 6H-SiC with varying field-plate length and gate-drain spacing were fabricated and analyzed. The classical small signal FET model and the well-known ColdFET method were used to extract the small signal parameters of the devices. Though the devices with field plates exhibited lower better f(T) characteristic, they did demonstrate better f(max), MSG and power density performances than the conventional devices without field plate. Besides, no independence of DC characteristic on field-plate length was observed. With the increase of the field-plate length and the gate-drain spacing, the characteristic of f(T) and f(max), degraded due to the large parasitic effects. Loadpull method was used to measure the microwave power performance of the devices. Under the condition of continuous wave at 5.4 GHz, an output power density of 4.69 W/mm was obtained for device with field-plate length of 0.5 mu m and gate-drain length of 2 mu m. (c) 2006 Elsevier Ltd. All rights reserved.

Evolution of mosaic structure in InN grown by metalorganic chemical vapor deposition

Mosaic structure in InN layers grown by metalorganic chemical vapor deposition at various temperatures has been investigated by X-ray diffraction (XRD). With a combination of Williamson-Hall measurement and fitting of twist angles, it was found that variation of growth temperature from 450 to 550 degrees C leads to the variation of the lateral coherence length, vertical coherence length, tilt and twist of mosaic blocks in InN films in a, respectively, monotonic way. In particular, mosaic tilt increases whereas mosaic twist decreases with elevating temperature. Atomic force microscopy shows the morphological difference of the InN nucleation layers grown at 450 and 550 degrees C. Different coalescence thickness and temperature-dependent in-plane rotation of InN nuclei are considered to account for the XRD results. (c) 2006 Elsevier B.V. All rights reserved.

Passively Q-switched and mode-locked diode-pumped Nd : YVO4 laser with LT-GaAs output coupler

We have demonstrated an efficient and compact passively Q-switched and mode-locked (QML) 1064 nm Nd:YVO4 laser by using a low temperature grown GaAs (LT-GaAs) saturable absorber as well as an output coupler. Stable QML with envelope duration as short as 10 ns and Q-switched repetition rate of 36 kHz was obtained. It is the shortest envelope duration as far as we know, and it is so short that it can be used as Q-switching pulses directly. At 6.9 W of the incident pump power, average output power of 1.24 W was achieved and the corresponding peak power and energy of a single Q-switched pulse were 3.44 kW and 34.4 mu J, respectively. The mode-locked pulses inside the Q-switched pulse envelope had a repetition rate of 780 MHz. (C) 2005 Elsevier B.V. All rights reserved.

Field-aided collection in GaInP2 top solar cells

This paper reports the study on a field-aided collection in p-on-n GaInP2 top cells. The cells were produced by metalorganic vapor phase epitaxy at a low gas pressure. In order to optimize the device configuration, numerical simulations have been performed for the impacts of field-aided collection on the performance of the top cells. On the basis of the modeling results, a modified p(+)-p(-)-n(-)-n(+) configuration is introduced for GaInP2 top cells. This modification has brought out improved photovoltaic performance of the top cells, with conversion efficiency EFF = 14.26% (AM0, 2 x 2 cm(2), 25degreesC). (C) 2003 Elsevier B.V. All rights reserved.

Fabrication of improved FD SOIMOSFETs for suppressing edge effect

FD SOI MOSFETs with MESA and Irradiated FD SOI MOSFETs with LOCOS isolation usually show the edge effect, that is, the leakage current called hump is generated in the subthreshold region. According to different reasons for generating the edge effect, rounded corner process and BTS structure are applied to improve device performance. The results indicate that the above two methods are effective to reduce the edge effect and qualified devices are fabricated successfully.

“中介逻辑”与Woodruff三值逻辑系统

在《“中介逻辑”的特征问题》一文里,我们对近来朱梧梗、肖奚安等同志发表的称为“中介逻辑”的命题系统MP的三个联接词(对立否定),～(模糊否定)与→(蕴含)建立了如下的三值真值表: