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1.
《Solid-state electronics》2006,50(7-8):1425-1429
Two alloyed ohmic contact structures for AlGaN/GaN–Ti/Al/Ti/Au and Ti/Al/Mo/Au were studied. Both structures were optimized for minimum ohmic contact resistance. Structures grown on sapphire and SiC substrates were used to investigate structural properties of ohmic contacts to AlGaN/GaN. Ohmic contacts to AlGaN/GaN on SiC showed higher contact resistance values compared to contacts to AlGaN/GaN on sapphire. Ohmic contact metals were etched on samples after annealing. The alloyed interface was studied with backside illumination under an optical microscope. Alloyed inclusions associated with threading dislocations were observed on the surface. For the AlGaN/GaN on SiC sample the inclusion density was an order of magnitude lower than for the sample on sapphire. Conductive atomic force microscopy with carbon nanotube tip was used to investigate topography and conductivity profile of the surface after ohmic contact metal removal by etching. 相似文献
2.
The features of the formation of Ta/Ti/Al/Mo/Au ohmic contacts to a Al0.26Ga0.74N/AlN/GaN heterostructure grown on semi-insulating Si(111) substrates are studied. The dependences of the contact resistance on the Al (90, 120, 150, 180 nm) and Ti (15, 30 nm) layer thickness and optimal temperature-time annealing conditions are determined for each studied metallization scheme. It is shown that the minimum achievable contact resistance monotonically increases from 0.43 to 0.58 Ω mm as the Al layer thickness increases from 90 to 180 nm at unchanged Ta, Ti, Mo, Au layer thicknesses. A change in the Ti layer thickness from 15 to 30 nm has no significant effect on the minimum contact resistance. The least contact resistance of 0.4 Ω mm is achieved for Ta/Ti/Al/Mo/Au layers with thicknesses of 10/15/90/40/25 nm, respectively. The optimal annealing temperature for this metallization variant is 825°C at a process duration of 30 s. The grown ohmic contacts have smooth contact-area edges and flat morphology of their surface. 相似文献
3.
The aim of this study is to improve the electrical properties of ohmic contacts that plays crucial role on the performance of optoelectronic devices such as laser diodes (LDs), light emitting diodes (LEDs) and photodetectors (PDs). The conventional (Pd/Ir/Au, Ti/Pt/Au and Pt/Ti/Pt/Au), Au and non-Au based rare earth metal-silicide ohmic contacts (Gd/Si/Ti/Au, Gd/Si/Pt/Au and Gd/Si/Pt) to p-InGaAs were investigated and compared each other. To calculate the specific contact resistivities the Transmission Line Model (TLM) was used. Minimum specific contact resistivity of the conventional contacts was found as 0.111 × 10−6 Ω cm2 for Pt/Ti/Pt/Au contact at 400 °C annealing temperature. For the rare earth metal-silicide ohmic contacts, the non-Au based Gd/Si/Pt has the minimum value of 4.410 × 10−6 Ω cm2 at 300 °C annealing temperature. As a result, non-Au based Gd/Si/Pt contact shows the best ohmic contact behavior at a relatively low annealing temperature among the rare earth metal-silicide ohmic contacts. Although the Au based conventional ohmic contacts are thermally stable and have lower noise in electronic circuits, by using the non-Au based rare earth metal-silicide ohmic contacts may overcome the problems of Au-based ohmic contacts such as higher cost, poorer reliability, weaker thermal stability, and the device degradation due to relatively higher alloying temperatures. To the best of our knowledge, the Au and non-Au based rare earth metal-silicide (GdSix) ohmic contacts to p-InGaAs have been proposed for the first time. 相似文献
4.
We have investigated and compared the characteristics of Au:Ge, Ni/Au:Ge and Au/Ni/Au:Ge ohmic contact metallizations to ion-implanted and epitaxial n-GaAs layers on semi-insulting substrates. Auger depth profiles of ohmic contacts and SEM of surface microstructures have provided significant insight as to the nature and degradation mechanism of ohmic contacts with aging. An electrolytic tank model with distributed resistors representing nodular or cluster form contacts has been successfully used to understand the effects of non-uniform ohmic contacts. A small degree of change in the semiconductor sheet resistance in the gaps between contacts, with aging at an elevated temperature, has been attributed to possible lateral surface diffusion of Au in the Au:Ge contacts and Ge in the Ni/Au:Ge and Au/Ni/Au:Ge contacts. 相似文献
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6.
Comparative analysis of the influence of thermal annealing on Ge/Au/Ni-, Ge/Au/Ti/Au-, and Ge/Au/Ni/Ti/Au-based ohmic contacts
and Ti/Au-based Schottky contacts deposited on an n-GaAs (100) surface treated and nontreated in (NH4)2S aqueous solution have been performed. Annealing conditions for ohmic contacts are found that lead to a decrease in the specific
contact resistance of sulfur-treated samples by a factor of 2.5–15 in comparison with the nontreated samples. Optimal annealing
conditions are also determined for sulfur-treated GaAs samples with Schottky contacts, which make it possible to reduce the
ideality factor and increase the barrier height and the breakdown voltage with respect to the nontreated samples. 相似文献
7.
Excellent annealed ohmic contacts based on Ge/Ag/Ni metallization have been realized in a temperature range between 385 and 500/spl deg/C, with a minimum contact resistance of 0.06 /spl Omega//spl middot/mm and a specific contact resistivity of 2.62 /spl times/10/sup -7/ /spl Omega//spl middot/cm/sup 2/ obtained at an annealing temperature of 425/spl deg/C for 60 s in a rapid thermal annealing (RTA) system. Thermal storage tests at temperatures of 215 and 250/spl deg/C in a nitrogen ambient showed that the Ge/Ag/Ni based ohmic contacts with an overlay of Ti/Pt/Au had far superior thermal stabilities than the conventional annealed AuGe/Ni ohmic contacts for InAlAs/InGaAs high electron mobility transistors (HEMTs). During the storage test at 215/spl deg/C, the ohmic contacts showed no degradation after 200 h. At 250/spl deg/C, the contact resistance value of the Ge/Ag/Ni ohmic contact increased only to a value of 0.1 /spl Omega//spl middot/mm over a 250-h period. Depletion-mode HEMTs (D-HEMTs) with a gate length of 0.2 /spl mu/m fabricated using Ge/Ag/Ni ohmic contacts with an overlay of Ti/Pt/Au demonstrated excellent dc and RF characteristics. 相似文献
8.
Dae-Woo Kim Jun Cheol Bae Woo Jin Kim Hong Koo Baik Cha Yeon Kim Wook Kim Yoon Ho Choi Chin-Kyo Kim Tae-Kyung Yoo Chang Hee Hong Sung-Man Lee 《Journal of Electronic Materials》2001,30(7):855-860
We have investigated the electrical properties and interfacial reactions of the Si/Ti-based ohmic contacts to Si-doped n-GaN grown by metal organic chemical vapor deposition and the electrical properties were related to the material reactions. Si/Ti contact system was selected because Ti silicides have a low work function comparable to Al and also Si was used widely as an n-type dopant. As the annealing temperature increased, the specific contact resistance of Si/Ti-based ohmic contacts decreased and showed minimum contact decreased and showed minimum contact resistance as low as 3.86 10?6 cm2 after annealing at 900°C for 3 min under N2 ambient. Our experimental results show that the ohmic behavior of Si/Ti-based contact, were attributed to the low barrier height of Ti-silicide/GaN interface, which was formed through the interfacial reaction between Si and Ti layers. In order to clarify the current conduction mechanism of Si/Ti-based contact, temperature dependent contact resistance measurement was carried out for Au(1000 Å)/Ti(400 Å)/Si(1500 Å)/Ti(150 Å) contact system after annealing at 700°C for 3 min. The contact resistance of Si/Ti-based ohmic contact decreased exponentially with the measuring temperature and so it can be concluded that current flows over the low barrier height by thermionic emission. 相似文献
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11.
《Electron Devices, IEEE Transactions on》1986,33(2):294-297
Ion implantation and rapid thermal annealing have been used to selectively produce thin high carrier concentration n- and p-type layers on In0.53 Ga0.47 As, and nonalloyed ohmic contacts with excellent properties have been achieved by depositing layers of Cr and Au on the implanted regions. The Cr/Au metallization is used to produce ohmic contacts on both p-type and n-type material in the same deposition. A series of electrical test patterns based on the transmission line model and four terminal structure were used to characterize the contact resistance of both alloyed and nonalloyed ohmic contact metallizations on In0.53 Ga0.47 As. The nonalloyed contacts to n-type material are superior to conventional alloyed contacts made in this study, while the nonalloyed contacts to p-type material are a factor of 5 higher resistance. 相似文献
12.
Burm J. Chu K. Schaff W.J. Eastman L.F. Khan M.A. Qisheng Chen Yang J.W. Shur M.S. 《Electron Device Letters, IEEE》1997,18(4):141-143
HFET's with 0.12-μm gate length were fabricated on a III-V nitride wafer. The contact resistance from unannealed Ti/Au ohmic contact was 10 Ω·mm. Even with this relatively high contact resistance, fT of 46.9 GHz and fmax of 103 GHz were measured with the Ti/Au contacts, the highest yet achieved on III-V nitride FETs. The improvement in the frequency response was mainly due to the decrease in the gate length (0.12 μm). In addition, the effects of high contact resistances at high frequency are discussed 相似文献
13.
Au/Zn/Au/p-In P欧姆接触的界面研究 总被引:2,自引:0,他引:2
研究了离子束溅射制备的Au/Zn/Au/p-InP欧姆接触的界面特性.在480℃退火15s比接触电阻达到最小,为1.4×1 0-5 Ω·cm 2.利用俄歇电子能谱(AES)和X射线光电子能谱(XPS)研究了接触界面的冶金性质.实验结果表明,在室温下InP中的In就可以扩散到接触的表面,退火后可与Au形成合金.退火后,Zn的扩散可以在p-InP表面形成重掺杂层,从而降低接触势垒高度,减小势垒宽度,有助于欧姆接触的形成;在接触与p-InP的界面产生一个P聚集区,同时Au与InP反应生成Au2P3,其P的2p3/2电子的结合能约为129.2 eV. 相似文献
14.
For the first time in Russia, the Si/Al/Ti/Au alloyed contact composition is investigated for the formation of ohmic contacts to AlGaN/GaN heterostructures using thermal annealing. The obtained results are compared with those for conventional Ti/Al/Ni/Au ohmic contacts. Use of the composition under investigation makes it possible to decrease the annealing temperature to 675–700°C, which results in improvement in the morphology of alloyed ohmic contacts in comparison with conventional contacts. The value of the contact resistance using the Si/Al-based composition to the AlGaN/GaN heterostructure is obtained in relation to the temperature and annealing duration. It is shown that no qualitative change in the resistance occurs at an annealing duration of several minutes in the temperature range of 700–750°C. In the temperature range of 675–700°C, there is an asymptotic decrease in the contact resistance with increasing annealing duration. The smallest value of the contact resistance amounts to 0.41 Ω mm. 相似文献
15.
Ping Jian Douglas G. Ivey Robert Bruce Gordon Knight 《Journal of Electronic Materials》1994,23(9):953-962
Two Pd-based metallizations have been systematically studied, i.e., Au/Ge/Pd and Pd/Ge contacts to n-type InP, in an attempt
to better understand the role of the metallization constituents in forming ohmic contacts. Ohmic contacts were obtained with
minimum specific resistances of 2.5 × 10−6 Ω-cm2 and 4.2 × 10−6 Ω-cm2 for the Au/Ge/Pd and the Pd/Ge contacts, respectively. The annealing regime for ohmic contact formation is 300-375°C for
the Au/Ge/Pd/InP system and 350-450°C for the Pd/GelnP system. Palladium, in both cases, reacts with InP to form an amorphous
layer and then an epitaxial layer at low temperatures, providing good metallization adhesion to InP substrates and improved
contact morphology. Ohmic contact formation in both contacts is attributed to Ge doping, based on the solid state reaction-driven
decomposition of an epitaxial layer at the metallization/InP interface, producing a very thin, heavily doped InP layer. Gold
appears to be responsible for the difference in contact resistance in the two systems. It is postulated that Au reacts strongly
with In to form Au-In compounds, creating additional In site vacancies in the InP surface region (relative to the Au-free
metallization), thereby enhancing Ge doping of the InP surface and lowering the contact resistance. Both contacts degrade
and ultimately become Schottky barriers again if over annealed, due to consumption of additional InP, which destroys the heavily
doped InP layer. 相似文献
16.
J. T. Trexler J. J. Fijol L. C. Calhoun R. M. Park P. H. Holloway 《Journal of Electronic Materials》1996,25(9):1474-1477
Formation and temperature stability of sputter deposited gold ohmic contacts to molecular beam epitaxially grown p-type ZnTe (doped with nitrogen to a free hole concentration of ≈3 × 1018 cm3) have been studied using current-voltage (I-V), Auger electron spectroscopy, secondary ion mass spectrometry, and optical and scanning electron microscopy. The I-V characteristics of ≈1500Å Au/p-ZnTe contacts were measured as-deposited and after heat treatments at 150, 200, 250, and 350°C for 15 min intervals up to 90 min. As deposited, the contacts were poor Schottky contacts, but became ohmic after 15 min at all temperatures. There was an increased resistance at t>15 min for T≤250°C, and a very large resistance increase upon heat treatment for all times at 350°C. The interface between the metallization and ZnTe was initially very planar, and remained planar upon formation of the ohmic contact. Upon heating at T>250°C, Au diffused into ZnTe. The ohmic behavior of the Au/p-ZnTe contacts is attributed to this diffusion which created a highly doped near-surface region in the ZnTe. Microscopy showed that Au also migrated across the ZnTe surface forming an extended reaction zone (≈100 μm) around the dot contact at T≥250°C. 相似文献
17.
We report here on the optimization of ohmic contacts to p-CuInSe2 (CISe) single crystals. A low resistance ohmic contact is required to minimize current losses due to series resistance; e.g.
in Schottky diodes. Both In-Ga (eutectic)/CISe and gold (evaporatedVCISe contacts have been fabricated on crystals with different
orientations and bulk properties. Gold contacts were found to have a lower resistance and to be more stable than In-Ga ones,
from the slope of the linear current-voltage plot of the junctions. The resistance of the Au/CISe ohmic contact was decreased
by etching the CISe crystal surface chemically in a 0.5% solution of Br2 in methanol for 30 sec at room temperature, prior to gold deposition, while that of the In-Ga contact increased by this etch.
Wetting experiments and contact angle measurements showed evidence for changes in the polarity of the surface due to chemical
etches. 相似文献
18.
This paper presents the optimization of polysilicon doping and metallization to form ohmic contact with etching resistance. Indeed, polysilicon doped by ion implantation and ohmic contacts are an important and interesting part of integrated circuit technology or MEMS and NEMS. LPCVD-polysilicon doping parameters, such as ion energy, dose, and annealing were investigated. In particular a superficial implantation realized after a deep implantation enables one to slightly decrease the polysilicon resistivity while the contact resistance is reduced. And ohmic contacts with wet etching resistance were realized by depositing the different metallization stacks. We demonstrate that ohmic contact pad Cr/Pt/Au has provided a good adhesion on LPCVD-polysilicon after wet etching. 相似文献
19.
Brian P. Downey Suzanne E. Mohney Trevor E. Clark Joseph R. Flemish 《Microelectronics Reliability》2010,50(12):1967-1972
The degradation produced by high current density stressing of a contact to p-SiC consisting of an Al-bearing ohmic contact, a TiW diffusion barrier, and a thick Au overlayer was studied. The test structure allowed for vertical current stressing and the measurement of the specific contact resistance before and after stressing. A threshold current for contact failure was established for the Ti/Al and W/Al contacts, at which a large increase in specific contact resistance was measured and extensive voiding occurred in the ohmic contact region. The high current stressing generated a flux of Al from the ohmic contact layer, through the TiW barrier, to the surface to be oxidized, along with a flux of Au into the ohmic contact layer. The voiding in the ohmic contact layer, caused by the unequal fluxes of Al and Au, decreased the active area of the contact, consequently increasing the current density and the associated effects from electromigration and Joule heating, initiating a runaway event. 相似文献