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The light enhancement of PhC LEDs within the collection cone angle was obtained according to measured far-field patterns. In a plusmn20deg collection cone, the collimated PhC LED was enhanced up to ~2.4.
In this paper, we investigated the field emission characteristics of diamond micropowders with sharp edges. The emission characteristics exhibited the Fowler-Nordheim relationship, and the edges of the diamond micropowders worked as field electron sources. We suggest that the increase in the emission current was caused by an increase in the active emission sites. The vacuum pressure had little influence...
GaN is a promising material for the high frequency, high power and high temperature electrical and optical ultraviolet devices due to its unique material parameters. The field and photofield emission may be developed as a method for determination of some of the band structure features. The peculiarities of electron field and photon-assisted field emission from GaN nanorods are presented here. The...
We investigated the effects of the growth parameters on the microstructural, optoelectronic and low-frequency noise properties of InGaN/GaN multiple quantum well (MQW). Dc current stress was applied to the devices and their degradations were investigated as a function of the stress time.
GaN-based low-noise amplifiers (LNAs) recently were shown to provide high ruggedness together with low noise figure. These LNAs allow for simplified receiver architectures, e.g., since no limiter is required to protect the input. This paper for the first time presents an investigation of the recovery time of a highly rugged GaN LNA. The X-band LNA is shown to survive input overdrive powers up to 46...
In this work we present an amorphous silicon/amorphous silicon carbide balanced photodiode structure suitable for differential photocurrent measurements in the ultraviolet (UV) and visible range. The device is a three-terminal structure constituted by two series-connected amorphous silicon p-i-n photodiodes. The structure takes advantage of the differential measurement to reveal very small variations...
This study presents extensive thermal characterization of GaN/SiC devices from five US sources across temperature (-25degC to +125degC). The changes with temperature for: cutoff frequency (ft), maximum oscillation frequency (fmax), saturated current (Idss), transconductance (gm) are measured, statistics studied, and correlations investigated. Temperature-coefficients are established for ft, fmax,...
The microwave plasma enhanced chemical vapor deposition technique has been employed to grow polycrystalline diamond films on p-doped Si (100) substrates starting from highly diluted (1% CH4 in H2) gas mixtures. Coplanar interdigitated Cr/Au contacts have been thermally evaporated on two samples about 8 mum thick having different grain size. Dark current-voltage (I-V) measurements and impedance characterization...
In this study, the laser lift-off (LLO) technique is used to fabricate the substrate-free InGaN thin-film solar cells (TF-SCs). The epitaxial structures consist of 8-pair In0.23Ga0.77N/GaN multiple-quantum-well (MQW), which is sandwiched between the p- and n-GaN to construct the conventional p-i (intrinsic layer)-n solar cells. After the LLO process to remove the sapphire substrate, a silver layer...
ITO/AZO double films were deposited by RF sputtering on p-Si texturized substrate to fabricate ITO/AZO/SiO2/p-Si SIS heterojunction. The structural, optics and electrical properties of the ITO/AZO films were characterized by UV-VIS spectrophotometer, four point probe, respectively. The results show that ITO/AZO films have good quality. The electrical junction properties were investigated by I-V measurement,...
To widen the variety of substrate choice of Cu(In, Ga)Se2 (CIGS) solar cells, a lift off process was developed without an intentional sacrifice layer between CIGS and Mo back contact layers. CIGS films grown on Mo/glass substrates were transferred to alternative substrates of glass and polyimide. Based on the transferred CIGS films, deices with ITO/ZnO/CdS/CIGS/Mo/epoxy/alternative-substrates structure...
We investigated the optical and electrical properties of amorphous InZnO (IZO) as a potential replacement of Al-doped ZnO (AZO) conducting window layer for CuInGaSe2 (CIGS) solar cells. The device performance of CIGS devices with IZO of different thickness and sheet resistance was compared with that of CIGS standard devices with AZO. The results show that the optical and electrical properties of IZO...
Lifetime measurements on single, packaged UV LEDs were performed under constant current injection at 20 and 75 mA (60 and 226 A/cm2). The junction temperature at operation was found by micro-Raman spectroscopy to be 57 and 184degC, respectively. Unbiased LEDs of similar characteristics placed in an oven baked at the equivalent operating junction temperatures showed a degradation in output power similar...
The present paper reports some computational measurements for the electrical properties of commercial Gallium Nitride blue light emitting diode (GaN blue LED). Many instruments have been used in this study to make different kinds of measurements. For example, Keithley 238 high current measure unit, Boonton 7200 capacitance meter, and wayne Kerr 6440 precision component analyzer ( within frequency...
This paper reports an analysis of the degradation of laser diodes for Blu-Ray technology. The study has been carried out by means of optical and electrical characterization techniques. We demonstrate that: (i) stress at constant current level determines the increase of the threshold current of the devices, and the decrease of the sub-threshold emission signal; (ii) degradation rate has an almost linear...
We demonstrate cascade green light-emitting-diode (LED) arrays, which have superior output-power to single LED without sacrificing modulation-bandwidth. 80 Mbit/sec eye-opening with a 0.65 mW coupled power to plastic-optical-fiber is achieved under the output of in-car battery (12 V).
The leakage current mechanism in Schottky contacts (SCs) to Al0.25Ga0.75N/GaN heterostructures incorporated by thin high-temperature (HT) AlN interlayer has been investigated using current-voltage measurements, atomic force microscopy, and deep level transient spectroscopy. The HT AlN interlayer thickness has a significant effect on the leakage current in SCs. The leakage current density is reduced...
This paper shows electrical characterizations and reliability analysis performed on AlGaN/GaN HEMTs processed on epitaxial layers grown on composite substrates. The results are very promising for the fabrication of low cost high power microwave transistors for wireless communication systems. The composite substrates constitute a valuable alternative to the silicon since better thermal properties are...
The paper reports microwave properties of AlGaN/GaN HEMT fabricated on sapphire substrate. The measured transition frequency as well as maximum frequency of oscillation was taken as a figure of merit for comparison of influence of different treatment. Using 2 mum length of gate electrode 7.425 GHz transition frequency as well as 23.437 GHz maximum frequency of oscillation was achieved. Significant...
We report a robust Q-band GaN MMIC LNA operating in the 42-47GHz frequency range using a 0.15 mum T-gate process. The measured noise figure of the MMIC is less than 3.1 dB over the band of interest and the NF has a minimum of 2.9 dB at a frequency of 45.5 GHz. The MMIC gain is between 19 and 20 dB across the band and the input return loss of the MMIC is less than -10 dB. The measured OIP3 of the MMIC...
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