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1.
Tantalum pentoxide (Ta2O5) deposited by pulsed DC magnetron sputtering technique as the gate dielectric for 4H-SiC based metal-insulator-semiconductor (MIS) structure has been investigated. A rectifying current-voltage characteristic was observed, with the injection of current occurred when a positive DC bias was applied to the gate electrode with respect to the n type 4H-SiC substrate. This undesirable behavior is attributed to the relatively small band gap of Ta2O5 of around 4.3 eV, resulting in a small band offset between the 4H-SiC and Ta2O5. To overcome this problem, a thin thermal silicon oxide layer was introduced between Ta2O5 and 4H-SiC. This has substantially reduced the leakage current through the MIS structure. Further improvement was obtained by annealing the Ta2O5 at 900 °C in oxygen. The annealing has also reduced the effective charge in the dielectric film, as deduced from high frequency C-V measurements of the Ta2O5/SiO2/4H-SiC capacitors. 相似文献
2.
Eiji MiyazakiYuji Goda Shigeru Kishimoto Takashi Mizutani 《Solid-state electronics》2011,62(1):152-155
AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistors (MOSHFETs) with Al2O3 gate oxide which was deposited by atomic layer deposition (ALD) were fabricated and their performance was then compared with that of AlGaN/GaN MOSHFETs with HfO2 gate oxide. The capacitance (C)-voltage (V) curve of the Al2O3/GaN MOS diodes showed a lower hysteresis and lower interface state density than the C-V curve of the HfO2/GaN diodes, indicating better quality of the Al2O3/GaN interface. The saturation of drain current in the ID-VGS relation of the Al2O3 AlGaN/GaN MOSHFETs was not as pronounced as that of the HfO2 AlGaN/GaN MOSHFETs. The gate leakage current of the Al2O3 MOSHFET was five to eight orders of magnitude smaller than that of the HfO2 MOSHFETs. 相似文献
3.
A stack of Al2O3/SiNx dual layer was applied for the back side surface passivation of p-type multi-crystalline silicon solar cells, with laser-opened line metal contacts, forming a local aluminum back surface field (local Al-BSF) structure. A slight amount of Al2O3, wrapping around to the front side of the wafer during the thermal atomic layer deposition process, was found to have a negative influence on cell performance. The different process flow was found to lead to a different cell performance, because of the Al2O3 wrapping around the front surface. The best cell performance, with an absolute efficiency gain of about 0.6% compared with the normal full Al-BSF structure solar cell, was achieved when the Al2O3 layer was deposited after the front surface of the wafer had been covered by a SiNx layer. We discuss the possible reasons for this phenomenon, and propose three explanations as the Ag paste, being hindered from firing through the front passivation layer, degraded the SiNx passivation effect and the Al2O3 induced an inversion effect on the front surface. Characterization methods like internal quantum efficiency and contact resistance scanning were used to assist our understanding of the underlying mechanisms. 相似文献
4.
《Organic Electronics》2014,15(4):835-843
TiO2 sols synthesized with a facile solution-based method were used as a buffer layer between the active layer and the cathode Al in conventional structure polymer solar cells (PSCs). Using transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray diffraction (XRD) and atomic force microscopy (AFM), the morphological and crystallographic properties of synthesized TiO2 nanoparticles (TiO2 NPs) as well as the buffer layer were studied in detail. It was observed that by increasing H2O in the process of peptization both the crystallinity and particle size of TiO2 NPs were enhanced, while the particles in sol showed a narrower size distribution conformed by dynamic light scattering. Inserting TiO2 NPs as a buffer layer in conventional structure PSCs, both the power conversion efficiency (PCE) and stability were improved dramatically. PSCs based on the structure of ITO/PEDOT:PSS/P3HT:PCBM/TiO2 NPs/Al showed the short-circuit current (Jsc) of 12.83 mA/cm2 and the PCE of 4.24%, which were improved by 31% and 37%, respectively comparing with the reference devices without a TiO2 buffer layer. The stability measurement showed that PSC devices with a TiO2 NPs buffer layer could retain 80% of the original PCEs after exposed in air for 200 h, much better than the devices without such a buffer layer. The effect can be attributed to the protection by the buffer layer against oxygen and H2O diffusion into the active layers. The observations indicate that TiO2 NPs synthesized by facile solution-based method have great potential applications in PSCs, especially for large-area printed PSCs. 相似文献
5.
Y.C. ChangM.L. Huang Y.H. ChangY.J. Lee H.C. ChiuJ. Kwo M. Hong 《Microelectronic Engineering》2011,88(7):1207-1210
Al2O3, HfO2, and composite HfO2/Al2O3 films were deposited on n-type GaN using atomic layer deposition (ALD). The interfacial layer of GaON and HfON was observed between HfO2 and GaN, whereas the absence of an interfacial layer at Al2O3/GaN was confirmed using X-ray photoelectron spectroscopy and transmission electron microscopy. The dielectric constants of Al2O3, HfO2, and composite HfO2/Al2O3 calculated from the C-V measurement are 9, 16.5, and 13.8, respectively. The Al2O3 employed as a template in the composite structure has suppressed the interfacial layer formation during the subsequent ALD-HfO2 and effectively reduced the gate leakage current. While the dielectric constant of the composite HfO2/Al2O3 film is lower than that of HfO2, the composite structure provides sharp oxide/GaN interface without interfacial layer, leading to better electrical properties. 相似文献
6.
Moonju Cho Amal AkheyarMarc Aoulaiche Robin DegraeveLars-Åke Ragnarsson Joshua TsengThomas Y. Hoffmann Guido Groeseneken 《Solid-state electronics》2011,62(1):67-71
Flat band voltage (VFB) roll-off in long channel devices at thin equivalent oxide thickness (EOT) is studied on SiO2/nitrided-HfSiO stacks. VFB increases when SiO2 interfacial layer thickness decreases, and charges pumping (CP) frequency sweep analysis shows higher trap density near Si/SiO2 interface. Based on this observation, an atomic diffusion model is introduced. Higher concentration of nitrogen atom in the HfSiO(N) layer diffuses to the Si/SiO2 interface through the SiO2 layer in thinner SiO2 device, and accumulates near Si/SiO2 interface which can introduce higher density of interfacial traps. Lifetime extracted from negative bias temperature instability (NBTI), and mobility are also degraded in thinner SiO2 devices due to the higher interfacial trap density.The VFB roll-off can be improved by lowering nitrogen concentration in the HfSiO(N) layer from optimizing plasma nitridation pressure, decreasing post deposition anneal temperature, or using defect absorbing layer on the high-k oxide. 相似文献
7.
Ki-Won KimSung-Dal Jung Dong-Seok KimKi-Sik Im Hee-Sung KangJung-Hee Lee Youngho BaeDae-Hyuk Kwon Sorin Cristoloveanu 《Microelectronic Engineering》2011,88(7):1225-1227
Normally-off GaN-MOSFETs with Al2O3 gate dielectric have been fabricated and characterized. The Al2O3 layer is deposited by ALD and annealed under various temperatures. The saturation drain current of 330 mA/mm and the maximum transconductance of 32 mS/mm in the saturation region are not significantly modified after annealing. The subthreshold slope and the low-field mobility value are improved from 642 to 347 mV/dec and from 50 to 55 cm2 V−1 s−1, respectively. The ID-VG curve shows hysteresis due to oxide trapped charge in the Al2O3 before annealing. The amount of hysteresis reduces with the increase of annealing temperature up to 750 °C. The Al2O3 layer starts to crystallize at a temperature of 850 °C and its insulating property deteriorates. 相似文献
8.
Perovskite solar cells (PSCs) with a simple device structure are particularly attractive due to their low cost and convenient fabrication process. Herein, highly efficient, electron-blocking layer (EBL)-free planar heterojunction (PHJ) PSCs with a structure of ITO/CH3NH3PbI3/PCBM/Al were fabricated via low-temperature, solution-processed method. The power conversion efficiency (PCE) of over 11% was achieved in EBL-free PHJ-PSCs, which is closed to the value of PSC devices with the PEDOT:PSS as the EBL. It is impressed that the open-circuit voltage (Voc) up to 1.06 V, an average value of 1.0 V for 43 devices, was obtained in EBL-free PHJ-PSCs. The electrochemical impedance spectroscopy (EIS) results suggested that the high PCE and Voc are attributed to the relatively large recombination resistance and low contact resistance in EBL-free PHJ-PSCs. The solution-processed, EBL-free PHJ structure paves a boulevard for fabricating high-efficiency and low-cost PSCs. 相似文献
9.
The SrAl2O4:Eu2+ phosphor powders have been synthesized by sol-gel process. Electroluminescent (EL) properties of the SrAl2O4:Eu2+ phosphor were investigated using a convenient thick film device. Green light emitting at a peak of 508 nm was obtained when driven by sine alternating current (AC). The color coordinate of the emission was x=0.148 and y=0.635. Luminance-voltage and afterglow characteristics of the SrAl2O4:Eu2+ EL devices were studied. The results show that SrAl2O4:Eu2+ can be used as green phosphor for EL displays. 相似文献
10.
《Organic Electronics》2014,15(8):1745-1752
The performance of both inverted and conventional polymer solar cells (PSCs) were examined with a low-temperature, solution-processed synthesized TiO2 nanoparticles (TiO2 NPs) as the electron extraction layer. The performance of inverted PSCs based on P3HT:PCBM bulk-heterojunction with a TiO2 NPs layer was dramatically improved and the highest power conversion efficiency (PCE) of 4.56% was achieved via 24 h exposure in air, which is one of the highest PCEs for P3HT:PCBM bulk-heterojunction PSCs using TiO2 as electron extraction layer. Meanwhile, the performance of inverted PSCs was superior to regular PSCs. Mott-Schottky capacitance analysis was carried out for both inverted and regular PSCs to obtain the built-in potential, the depletion width, as well as the doping level of the active layer, which all support the performance improvement of PSCs devices with inverted structure. In addition, inverted PSCs show excellent stability in air without encapsulation. The PCE can retain 87% of its original values after 400 h exposure in air, which is much better than that of regular PSCs. The results indicate that solution-processed TiO2 NPs shows great potential applications in the fabrication of highly efficient and stable inverted PSCs as well as large-area, flexible printed PSCs. 相似文献
11.
Yung-Hsien Wu Lun-Lun ChenWei-Chia Chen Chia-Chun LinMin-Lin Wu Jia-Rong Wu 《Microelectronic Engineering》2011,88(7):1361-1364
A Ge-stabilized tetragonal ZrO2 (t-ZrO2) film with permittivity (κ) of 36.2 was formed by depositing a ZrO2/Ge/ZrO2 laminate and a subsequent annealing at 600 °C, which is a more reliable approach to control the incorporated amount of Ge in ZrO2. On Si substrates, with thin SiON as an interfacial layer, the SiON/t-ZrO2 gate stack with equivalent oxide thickness (EOT) of 1.75 nm shows tiny amount of hysteresis and negligible frequency dispersion in capacitance-voltage (C-V) characteristics. By passivating leaky channels derived from grain boundaries with NH3 plasma, good leakage current of 4.8 × 10−8 A/cm2 at Vg = Vfb − 1 V is achieved and desirable reliability confirmed by positive bias temperature instability (PBTI) test is also obtained. 相似文献
12.
The feasibility of employing yttrium oxide (Y2O3) as high-k gate dielectrics for GaAs metal-oxide-semiconductor (MOS) devices has been investigated. MOS capacitors were fabricated using RF-sputtered deposited Y2O3 films on NH4OH treated n-GaAs substrate. Indeed high-k (Y2O3)/GaAs MOS capacitors exhibiting fairly good electrical characteristics, for instance, especially low leakage current density, low hysteresis and allowable density of interface states, have been achieved. The effects of several annealing treatments on Y2O3-gated GaAs MOS capacitors have been investigated in order to optimize the process conditions. A decrease in accumulation capacitance (Cacc) following PDA effectively increases the equivalent oxide thickness (EOT), which is predicted to be correlated with the growth and continuous increase in the physical thickness of a lower-k inter-layer sandwiched between Y2O3 and GaAs. However, leakage currents and interface trap densities are reduced with higher values of annealing temperature. The variation of current density with an equivalent oxide thickness (EOT) has also been investigated. 相似文献
13.
Kwang-Ho Kwon Jun-Kyu Yang Ho Jung Chang Hyung-Ho Park 《Microelectronic Engineering》2008,85(8):1781-1785
Yttrium was deposited on the chemical oxide of Si and annealed under vacuum to control the interface for the formation of Y2O3 as an insulating barrier to construct a metal-ferroelectric-insulator-semiconductor structure. Two different pre-annealing temperatures of 600 and 700 °C were chosen to investigate the effect of the interface state formed after the pre-annealing step on the successive formation of Y2O3 insulator and Nd2Ti2O7 (NTO) ferroelectric layer through annealing under an oxygen atmosphere at 800 °C. Pre-anneal treatments of Y-metal/chemical-SiO2/Si at 600 and 700 °C induced a formation of Y2O3 and Y-silicate, respectively. The difference in the pre-anneal temperature induced almost no change in the electrical properties of the Y2O3/interface/Si system, but degraded properties were observed in the NTO/Y2O3/interface/Si system pre-annealed at 600 °C when compared with the sample pre-annealed at 700 °C. C-V characteristics of the NTO/Y2O3/Si structured system showed a clockwise direction of hysteresis, and this gap could be used as a memory window for a ferroelectric-gate. A smaller hysteric gap and electrical breakdown values were observed in the NTO/Y2O3/Si system pre-annealed at 600 °C, and this was due to an unintentional distribution of the applied field from the presence of an interfacial layer containing Y-silicate and SiO2 phases. 相似文献
14.
Electrical properties of mixed HfO2-Ta2O5 films (10;15 nm) deposited by rf sputtering on Si have been studied from the view point of their applications as high-k layers, by standard capacitance-voltage and temperature dependent current-voltage characteristics. The effect of HfO2 addition to the Ta2O5 is thickness dependent and the thicker layers exhibit advantages over the pure Ta2O5 (higher dielectric constant, enhanced charge storage density and improved interface quality). The process of HfO2 and Ta2O5 mixing introduces negative oxide charge, tends to creates shallow bulk traps and modifies the dominant conduction mechanisms in the stack capacitors as compared to the Ta2O5-based one (a contribution of tunneling processes through traps located below the conduction band of mixed layers to the leakage current in the HfO2-Ta2O5 stacks is observed). The traps involved in both Poole-Frenkel and tunneling processes are identified. 相似文献
15.
分别采用旋涂法和水热法在FTO衬底上制备Co3O4种子层和Co3O4薄膜,再在Co3O4薄膜上水热生长Fe2O3纳米棒,获得了高质量的Co3O4/Fe2O3异质结复合材料。通过改变Fe2O3前驱体溶液浓度来改变异质结复合材料中Fe2O3组分的含量。结果表明,Fe2O3纳米棒覆盖在呈网状结构的Co3O4薄膜上,随着Fe2O3前驱体溶液浓度即Fe2O3组分含量的增加,Co3O4/Fe2O3异质结复合材料对紫外光的响应逐渐增强,当Fe2O3前驱体溶液浓度为0.015mol/L时,异质结复合材料有着很好的光电稳定性,并表现出较高的响应率(12.5mA/W)和探测率(4.4×1010Jones)。 相似文献
16.
Hafnium oxide (HfO2) films were deposited on Si substrates with a pre-grown oxide layer using hafnium chloride (HfCl4) source by surface sol-gel process, then ultrathin (HfO2)x(SiO2)1−x films were fabricated due to the reaction of SiO2 layer with HfO2 under the appropriate reaction-anneal treatment. The observation of high-resolution transmission electron microscopy indicates that the ultrathin films show amorphous nature. X-ray photoelectron spectroscopy analyses reveal that surface sol-gel derived ultrathin films are Hf-Si-O alloy instead of HfO2 and pre-grown SiO2 layer, and the composition was Hf0.52Si0.48O2 under 500 °C reaction-anneal. The lowest equivalent oxide thickness (EOT) value of 0.9 nm of film annealed at 500 °C has been obtained with small flatband voltage of −0.31 V. The experimental results indicate that a simple and feasible solution route to fabricate (HfO2)x(SiO2)1−x composite films has been developed by means of combination of surface sol-gel and reaction-anneal treatment. 相似文献
17.
L. Lamagna M. FusiS. Spiga M. Fanciulli G. BrammertzC. Merckling M. MeurisA. Molle 《Microelectronic Engineering》2011,88(4):431-434
In this work we investigate the effect of different III-V surface passivation strategies during atomic layer deposition of Al2O3. X-ray photoelectron spectroscopy indicates that bare As-decapped and sulfur passivated In0.53Ga0.47As present residual oxides on the surface just before the beginning of the Al2O3 deposition while the insertion of a Ge interface passivation layer results in an almost oxide free Ge/III-V interface. The study of the initial growth regimes, by means of in situ spectroscopic ellipsometry, shows that the growth of Al2O3 on Ge leads to an enhanced initial growth accompanied by the formation of Ge-O-Al species thus affecting the final electrical properties of the stack. Alternatively, deposition on decapped and S-passivated In0.53Ga0.47As results in a more controlled growth process. The sulfur passivation leads to a better electrical response of the capacitor that can be associated to a lower oxide/semiconductor interface trap density. 相似文献
18.
Gelatin is a natural protein, which works well as the gate dielectric for pentacene/N,N-dioctyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-C8) ambipolar organic field-effect transistors (OFETs) in air ambient and in vacuum. An aqueous solution process was used to form the gelatin gate dielectric film on poly(ethylene terephthalate) (PET) by spin-coating and subsequent casting. Pentacene morphology and interface roughness are two major factors affecting the electron and hole field-effect mobility (μFE) values of pentacene/PTCDI-C8 ambipolar OFETs in vacuum and in air ambient. In contrast, water absorption in gelatin has higher contribution to the electron and hole μFE values in air ambient. The ambipolar performance of pentacene/PTCDI-C8 ambipolar OFETs depends on their layer sequence. For example, when PTCDI-C8 is deposited onto pentacene, i.e. in the structure of PTCDI-C8/pentacene, unbalanced ambipolar characteristics appear. In contrast, better ambipolar performance occurs in the structure of pentacene/PTCDI-C8. The optimum ambipolar characteristics with electron μFE of 0.85 cm2 V−1 s−1 and hole μFE of 0.95 cm2 V−1 s−1 occurs at the condition of pentacene (40 nm)/PTCDI-C8 (40 nm). Surprisingly, water absorption plays a crucial role in ambipolar performance. The device performance changes tremendously in pentacene/PTCDI-C8 ambipolar OFETs due to the removal of water out of gelatin in vacuum. The optimum ambipolar characteristics with electron μFE of 0.008 cm2 V−1 s−1 and hole μFE of 0.007 cm2 V−1 s−1 occurs at the condition of pentacene (65 nm)/PTCDI-C8 (40 nm). The roles of layer sequence, relative layer thickness, and water absorption are proposed to explain the ambipolar performance. 相似文献
19.
D. Tsoutsou A. Debernardi S.N. Volkos S. Schamm M. Fanciulli 《Microelectronic Engineering》2008,85(12):2411-2413
Rare earth oxides (REOs) have lately received extensive attention in relation to the continuous scaling down of non-volatile memories (NVMs). In particular, La2O3 films are promising for integration into future NVMs because they are expected to crystallize above 400 °C in the hexagonal phase (h-La2O3) which has a higher κ value than the cubic phase (c-La2O3) in which most of REOs crystallize. In this work, La2O3 films are grown on Si by atomic layer deposition using La(C5H5)3 and H2O. Within the framework of the h-La2O3 formation, we systematically study the crystallographic evolution of La2O3 films versus annealing temperature (200-600 °C) by Fourier transform infrared spectroscopy (FTIR) and grazing incidence X-ray diffraction (GIXRD). As-grown films are chemically unstable in air since a rapid transformation into monoclinic LaO(OH) and hexagonal La(OH)3 occurs. Vacuum annealing of sufficiently thick (>100 nm) La(OH)3 layers induces clear changes in FTIR and GIXRD spectra: c-La2O3 gradually forms in the 300-500 °C range while annealing at 600 °C generates h-La2O3 which exhibits, as inferred from our electrical data, a desirable κ ∼ 27. A quick transformation from h-La2O3 into La(OH)3 occurs due to H2O absorption, indicating that the annealed films are chemically unstable. This study extends our recent work on the h-La2O3 formation. 相似文献
20.
Sanghun JeonSungho Park 《Microelectronic Engineering》2011,88(6):872-876
In this study, the interface trap density of metal-oxide-semiconductor (MOS) devices with Pr2O3 gate dielectric deposited on Si is determined by using a conductance method. In order to determine the exact value of the interface trap density, the series resistance is estimated directly from the impedance spectra of the MOS devices. Subsequently, the dispersion characteristics are numerically analyzed on the basis of a statistical model. Lastly, the process-dependent interface trap density of Pr2O3 is evaluated. It is concluded that high-pressure annealing and a superior quality interfacial SiO2 layer are of crucial importance for achieving a sufficiently low interface trap density. 相似文献