scholarly journals Vertical Leakage in GaN-on-Si Stacks Investigated by a Buffer Decomposition Experiment

Micromachines ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 101
Author(s):  
Alaleh Tajalli ◽  
Matteo Borga ◽  
Matteo Meneghini ◽  
Carlo De Santi ◽  
Davide Benazzi ◽  
...  
Keyword(s):  
Positive Charge ◽  
Defect Density ◽  
Charge Trapping ◽  
Breakdown Field ◽  
Silicon Substrates ◽  
Nucleation Layer ◽  
Uniform Sample ◽  
The Difference ◽  
Vertical Leakage ◽  
Gan On Si

We investigated the origin of vertical leakage and breakdown in GaN-on-Si epitaxial structures. In order to understand the role of the nucleation layer, AlGaN buffer, and C-doped GaN, we designed a sequential growth experiment. Specifically, we analyzed three different structures grown on silicon substrates: AlN/Si, AlGaN/AlN/Si, C:GaN/AlGaN/AlN/Si. The results demonstrate that: (i) the AlN layer grown on silicon has a breakdown field of 3.25 MV/cm, which further decreases with temperature. This value is much lower than that of highly-crystalline AlN, and the difference can be ascribed to the high density of vertical leakage paths like V-pits or threading dislocations. (ii) the AlN/Si structures show negative charge trapping, due to the injection of electrons from silicon to deep traps in AlN. (iii) adding AlGaN on top of AlN significantly reduces the defect density, thus resulting in a more uniform sample-to-sample leakage. (iv) a substantial increase in breakdown voltage is obtained only in the C:GaN/AlGaN/AlN/Si structure, that allows it to reach VBD > 800 V. (v) remarkably, during a vertical I–V sweep, the C:GaN/AlGaN/AlN/Si stack shows evidence for positive charge trapping. Holes from C:GaN are trapped at the GaN/AlGaN interface, thus bringing a positive charge storage in the buffer. For the first time, the results summarized in this paper clarify the contribution of each buffer layer to vertical leakage and breakdown.

Buffer Thickness Contribution to Suppress Vertical Leakage Current With High Breakdown Field (2.3 MV/cm) for GaN on Si

2011 ◽  
Vol 32 (11) ◽  
pp. 1534-1536 ◽  
Author(s):  
Iruthayaraj Beaula Rowena ◽  
Susai Lawrence Selvaraj ◽  
Takashi Egawa
Keyword(s):  
Leakage Current ◽  
Breakdown Field ◽  
Vertical Leakage ◽  
Gan On Si

scholarly journals Superior photo-carrier diffusion dynamics in organic-inorganic hybrid perovskites revealed by spatiotemporal conductivity imaging

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Xuejian Ma ◽  
Fei Zhang ◽  
Zhaodong Chu ◽  
Ji Hao ◽  
Xihan Chen ◽  
...  
Keyword(s):  
Thin Films ◽  
Solar Cell ◽  
Relaxation Times ◽  
Charge Trapping ◽  
Free Carrier ◽  
Carrier Dynamics ◽  
Electron Hole ◽  
Inorganic Hybrid ◽  
Diffusion Dynamics ◽  
The Difference

AbstractThe outstanding performance of organic-inorganic metal trihalide solar cells benefits from the exceptional photo-physical properties of both electrons and holes in the material. Here, we directly probe the free-carrier dynamics in Cs-doped FAPbI3 thin films by spatiotemporal photoconductivity imaging. Using charge transport layers to selectively quench one type of carriers, we show that the two relaxation times on the order of 1 μs and 10 μs correspond to the lifetimes of electrons and holes in FACsPbI3, respectively. Strikingly, the diffusion mapping indicates that the difference in electron/hole lifetimes is largely compensated by their disparate mobility. Consequently, the long diffusion lengths (3~5 μm) of both carriers are comparable to each other, a feature closely related to the unique charge trapping and de-trapping processes in hybrid trihalide perovskites. Our results unveil the origin of superior diffusion dynamics in this material, crucially important for solar-cell applications.

Charge-Transfer Dipoles at the Si-SiO2 Interface and the Metal-Semiconductor Worfunction Difference In Mos Devices.

1987 ◽  
Vol 105 ◽  
Author(s):  
Hisham Z. Massoud
Keyword(s):  
Dipole Moment ◽  
Charge Transfer ◽  
Dipole Moments ◽  
Silicon Substrates ◽  
Interface Dipole ◽  
Mos Devices ◽  
Flatband Voltage ◽  
The Difference ◽  
Definition Of ◽  
Mos Structures

AbstractThe magnitude of the dipole moment at the Si-SiO2 interface resulting from partial charge transfer that takes place upon the formation of interface bonds has been calculated. The charge transfer occurs because of the difference in electronegativity between silicon atoms and SiO2 molecules which are present across the interface. Results obtained for (100) and (111) silicon substrates indicate that the magnitude of the interface dipole moment is dependent on substrate orientation and the interface chemistry. Dipole moments at the Si-SiO2 and gate-SiO2 interfaces should be included in the definition of the flatband voltage VFB of MOS structures. CV-based measurements of the metal-semiconductor workfunction difference φms on (100) and (111) silicon oxidized in dry oxygen and metallized with Al agree with the predictions of this model. Other types of interface dipoles and their processing dependence are briefly discussed.

2. Adhesion of the plasma-polymerized fluorocarbon films to silicon substrates The adhesion properties of the plasma-polymerized FC coatings were determined by using a test, already employed by Yasuda and Sharma [13] (see Fig. 1 and Table 1) in which the silicon substrates coated with plasma FC-films were boiled in a0.9% sodium chloride solution. The FC thin films produced in the processes 1 and 2 were lifted after a very short time (15 minutes). Coatings generated in process 3 were lifted after the second cycle of boiling. The films produced in processes 4 and 5 withstood the complete test procedure. The results are shown in Fig. 3. The poor adhesion of the polymerized films in the first two processes is due to the fact that these processes do not involve a plasma pre-treatment process. The difference between processes 1 and 3 is only in the plasma pre-treatment (process 1 does not contain the pre-treatment step of the silicon surface). The fluorocarbon films deposited by processes 4 and 5 have shown the best adhesion. These test results indicate that the plasma pre-treatment is very important and necessary for a good adhesion of the FC coatings to the silicon surfaces. 2.3. Patterning of FC films 2.3.1. Patterning through resist mask. The patterning of the FC films through a photoresist mask (conventional All resist AR-P351) was examined after deposition for process No. 5. Different coating parameters were investigated to improve the adhesion of the resist to the FC surface. The best adhesion results were obtained using the process parameters, shown in Table 3. Differences in the thickness uniformity of so-deposited resists were in a range below 5%. The samples were etched in a pure oxygen plasma in an RIE-system after the lithography steps (pre-bake, exposure, development, post-bake). A resolution of 2 /xm was obtained. A significant increase in the surface energy was not observed after resist stripping. The sessile contact angle of water was 103°. 2.3.2. Lift-off process for patterning thin plasma polymerized FC films. A lift-off process was also examined to pattern the thin FC films. The lithography steps were used before the plasma polymerization process was carried out (Fig. 2). A standard resist AR-P351 was coated directly onto the Si substrates. After all lithography

2014 ◽  
pp. 275-278
Keyword(s):  
Treatment Process ◽  
Test Procedure ◽  
Silicon Surfaces ◽  
Silicon Substrates ◽  
Fluorocarbon Films ◽  
Si Substrates ◽  
Complete Test ◽  
The Difference ◽  
Pre Treatment ◽  
Lift Off

scholarly journals A Comparative Study between the Effects of Magnetic and Nonmagnetic Dopants on the Properties of ZnO Varistors

2010 ◽  
Vol 2010 ◽  
pp. 1-9 ◽  
Author(s):  
A. Sedky ◽  
E. El-Suheel
Keyword(s):  
Comparative Study ◽  
Nonlinear Coefficient ◽  
Xrd Analysis ◽  
Breakdown Field ◽  
Doping Content ◽  
Leakage Currents ◽  
Electrical Conductivities ◽  
Zno Varistors ◽  
The Difference ◽  
Zno Ceramics

A comparative study between effects of Mn and Al on the properties of ZnO varistor sintered at 1200 is investigated by XRD, SEM hardness, and I-V measurements. Although both Mn and Al do not influence the well-known peaks related to wurtzite structure of ZnO ceramics, some other unknown peaks could be formed at higher doping content (). Also, the shape and size of grains are clearly different for both dopants. Average crystalline diameters, deduced from XRD analysis, are between 42 nm and 62 nm, which are 50 times lower than those obtained from SEM micrographs, while the oxygen vacancies deduced from EDAX analysis, are gradually decreased by doping content for both dopants. Interestingly, the values of breakdown field, nonlinear coefficient and barrier height are found to be higher in Mn samples as compared to Al samples, while the opposite is reported for leakage currents, hardness, and electrical conductivities. The values of are changed from 2.67 V/cm to 41.67 V/cm for Al, and from 1928 V/cm to 6571 V/cm for Mn. The conductivity of Al samples is higher than that of ZnO, and it is nearly (103–105) times the conductivity of Mn samples. These results are discussed in terms of the difference of magnetic moment and valence state between these two additives.

Crystal-Axis-Rotation of Laser-Recrystallized Silicon on Insulator

1989 ◽  
Vol 164 ◽  
Author(s):  
K. Sugahara ◽  
T. Ippóshi ◽  
Y. Inoue ◽  
T. Nishimura ◽  
Y. Akasaka
Keyword(s):  
Thermal Conductivity ◽  
Laser Power ◽  
Rotation Angle ◽  
Defect Density ◽  
Silicon On Insulator ◽  
Bottom Surface ◽  
Crystal Axis ◽  
Scan Speed ◽  
The Difference ◽  
Axis Rotation

AbstractThe relation between the seed pitch and defect density of the laserrecrystallized SOI film was investigated. It was found that the defect density of the SOI increases as the seed pitch increases. The dependences of the laser scan speed and laser power on rotation angle of the SOI film were experimentally and numerically investigated. The crystal-axisrotation of the SOI film was considered to be due to the difference of the temperature between the top and bottom surface of the SOI film near the liquid-solid interface. A polysilicon heat sink structure with high thermal conductivity was newly proposed and was found to reduce the rotation in a small angle.

scholarly journals Development of Catalytic-CVD SiNx Passivation Process for AlGaN/GaN-on-Si HEMTs

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 842 ◽  
Author(s):  
Myoung-Jin Kang ◽  
Hyun-Seop Kim ◽  
Ho-Young Cha ◽  
Kwang-Seok Seo
Keyword(s):  
Chemical Vapor ◽  
Drain Current ◽  
High Electron Mobility Transistors ◽  
Breakdown Field ◽  
High Electron ◽  
Electron Mobility Transistors ◽  
Current Collapse ◽  
Passivation Process ◽  
Gan On Si ◽  
Sinx Film

We optimized a silicon nitride (SiNx) passivation process using a catalytic-chemical vapor deposition (Cat-CVD) system to suppress the current collapse phenomenon of AlGaN/GaN-on-Si high electron mobility transistors (HEMTs). The optimized Cat-CVD SiNx film exhibited a high film density of 2.7 g/cm3 with a low wet etch rate (buffered oxide etchant (BOE) 10:1) of 2 nm/min and a breakdown field of 8.2 MV/cm. The AlGaN/GaN-on-Si HEMT fabricated by the optimized Cat-CVD SiNx passivation process, which had a gate length of 1.5 μm and a source-to-drain distance of 6 μm, exhibited the maximum drain current density of 670 mA/mm and the maximum transconductance of 162 mS/mm with negligible hysteresis. We found that the optimized SiNx film had positive charges, which were responsible for suppressing the current collapse phenomenon.

Role of electron injection on vertical leakage in GaN-on-Si epitaxial layers

2019 ◽  
Vol 128 ◽  
pp. 199-203 ◽  
Author(s):  
Chunyan Song ◽  
Xuelin Yang ◽  
Panfeng Ji ◽  
Jun Tang ◽  
Anqi Hu ◽  
...  
Keyword(s):  
Electron Injection ◽  
Epitaxial Layers ◽  
Vertical Leakage ◽  
Gan On Si
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