Download or read book Thermally Stable Ohmic and Schottky Contacts to GaN written by Lars Fredrik Voss and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: This dissertation is focused on the development of Ohmic and Schottky contacts to both nand p-type Gallium Nitride for use in microelectronic and optical devices. The goal is to develop low resistance contacts with greater thermal budgets and superior thermal aging characteristics to those commonly in use today as well as to understand the mechanisms by which these contacts may fail. In addition, p-type Ohmic contacts have been used to fabricate light emitting diodes (LEDs) which display far superior aging properties than those made with conventional Ni/Au contacts. Ohmic contacts to p-GaN were fabricated using a variety of refractory materials. The materials examined were of three basic types: boride, nitride, and the refractory metal Ir. The boride family includes W2B, W2B5, CrB2, ZrB2, and TiB2. The nitrides examined were TaN, TiN, and ZrN. Contacts based on these materials were fabricated using either a GaN//Ni/Au/X/Ti/Au, GaN//X/Ti/Au, or GaN//Ni/X/Au scheme, where X is the refractory material. Contact resistances as low as ~1 x 10-4 ohm/cm2 were consistently achieved after annealing at temperatures from 500-1000°C for 60 s in N2 using these materials for p-GaN with a carrier concentration of ~1 x 1017 cm-3.
Download or read book Development of High Temperature Stable Ohmic and Schottky Contacts on N GaN written by Rohit Khanna and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The contacts formed gave specific contact resistance of the order of 10−5 to 10−6 Ohm-cm2. A minimum contact resistance of 1.5x10−6 Ohm.cm2 was achieved for the TiB2 based scheme at an annealing temperature of 850-900 degreeC, which was comparable to a regular ohmic contact of Ti/Al/Ni/Au on n GaN. When some of borides contacts were placed on a hot plate or in hot oven for temperature ranging from 200 degreeC to 350 degreeC, the regular metallization contacts degraded before than borides ones. Even with a certain amount of intermixing of the metallization scheme the boride contacts showed minimal roughening and smoother morphology, which, in terms of edge acuity, is crucial for very small gate devices.
Download or read book Technology and Thermal Stability of ALGAN GAN HFETs written by and published by . This book was released on 1910 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: New approaches towards high reliable thermal stable ohmic and Schottky contacts for GaN/AlGaN-HFETs have been developed and implemented in device structures. The contact technology has been systematically optimized towards i) good electrical properties, ii) superior contact morphology and contour definition and Hi) high reliability and thermal stability. HFETs employing source/drain contacts based on WSiN diffusion barriers sandwiched between an Ti/Al/Ti/Au internal layer system and an overlayer metal as well as WSiN/Au and Ir/Au gate contacts have demonstrated long term stability at 400°C, Even after temperature storage tests at 500°C no significant device degradation could be detected. Ir/Au Schottky gates have found to be stable at the rather high level of Schottky barrier height of about 1.1 eV resulting in dramatically reduced leakage currents as compared to standard Pt/Ti/Au gate contacts to GaN-HFETs.
Download or read book Theoretical and Experimental Approach to Developing Improved Electrical Contacts to GaN written by and published by . This book was released on 1999 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The metallurgy and electrical performance of contacts to GaN were examined. Thermodynamic estimates coupled with experimental work revealed clear trends in the nature of the contact metallurgy depending upon the position of the metal in the periodic table. This information was then used to aid in the investigation and design of electrical contacts to GaN. Ohmic contacts to n-GaN, Schottky barriers to n-GaN, and ohmic contacts to p-GaN were fabricated and characterized. These studies resulted in an improved understanding of the mechanism of ohmic contact formation in Al/Ti/n-GaN contacts, along with the development of TiN/Ti/n-GaN and ZrN/Zr/n-GaN ohmic contacts with exceptional thermal stability at 600 deg C and contact resistivities of 6 x 10(exp -6) and 2 x 10(exp -5) ohm.sq cm, respectively, for n = 7 x 10(exp 17) cu cm. Also developed were Re/n-GaN Schottky barrier contacts that were stable upon annealing at 700 deg C with current-voltage and capacitance-voltage barrier heights of 0.82 and 1.06 eV, respectively. For ohmic contacts to p-GaN, a large number of contacts were evaluated. A clear improvement over conventional Au/Ni/p-GaN contacts was provided by electrodeposited Pt/p-GaN and sputtered Pt/Ni/p-GaN contacts, which provided contact resistivities that were lower than Au/Ni/p-GaN contacts by more than a factor of two. An explanation for this improvement was formulated.
Download or read book GaN and Related Materials II written by Stephen J. Pearton and published by CRC Press. This book was released on 2000-10-31 with total page 724 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first GaN and Related Materials covered topics such as a historical survey of past research, optical electrical and microstructural characterization, theory of defects, bulk crystal growth, and performance of electronic and photonic devices. This new volume updates old research where warranted and explores new areas such as UV detectors, microwave electronics, and Er-doping. This unique follow-up features contributions from leading experts that cover the full spectrum of growth.
Download or read book Ohmic Contacts to Semiconductors written by Electrochemical Society and published by . This book was released on 1969 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ohmic Contacts to GaN written by Douglas B. Ingerly and published by . This book was released on 2000 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Handbook of Refractory Carbides Nitrides written by Hugh O. Pierson and published by William Andrew. This book was released on 1996-12-31 with total page 363 pages. Available in PDF, EPUB and Kindle. Book excerpt: Refractory carbides and nitrides are useful materials with numerous industrial applications and a promising future, in addition to being materials of great interest to the scientific community. Although most of their applications are recent, the refractory carbides and nitrides have been known for over one hundred years. The industrial importance of the refractory carbides and nitrides is growing rapidly, not only in the traditional and well-established applications based on the strength and refractory nature of these materials such as cutting tools and abrasives, but also in new and promising fields such as electronics and optoelectronics.
Download or read book Advanced Process Development for Contacts to Algan gan High Electron Mobility Transistors HEMTS written by Benedict C. Ofuonye and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: High work function metals--Ni, Pt, Ir, and Au--were comparatively studied as Schottky metallizations to GaN and AlGaN/GaN heterostructures. Ni/Au, Ni/Pt/Au, Ir/Au, Ir/Pt/Au and Pt/Au Schottky diodes were fabricated on GaN and AlGaN/GaN substrates. Schottky barrier heights ranging from 0.8 to 0.9 eV were obtained as-deposited on GaN with ideality factors of about 1.05. The quality of the Schottky diodes was evaluated and their thermal stability also was studied. The interposition of Pt in Ni/Au and Ir/Au systems was found to improve the characteristics of the Schottky diodes. Ir/Pt/Au diodes were found to be more thermally stable than Ni/Pt/Au diodes. Ni/Au Schottky contacts exhibited good leakage response under thermal annealing for long periods. Microstructural studies were carried out on Ni/Pt/Au and Ni/Au Schottky contacts to elucidate the role of the intermediate layer, Pt, in the degradation of the Ni/Pt/Au metallization under long-term thermal anneal. A selective-area silicon ion implantation process for ohmic contact resistance improvement to AlGaN/GaN high electron mobility transistors (HEMTs) was developed. Non-alloyed ohmic contacts with very low contact resistances of 0.2 - 0.24 -mm were achieved with TLM pads fabricated using the Mo/Al/Mo/Au metallization. Simulations were carried out with SRIM to qualify the implantation process. Surface chemistry analysis was undertaken on the implanted AlGaN/GaN and GaN samples to determine the impact of implantation on the surface morphology of the AlGaN layer. The developed ion-implantation process was used to propose fabrication schemes for novel high speed self-aligned and non-self-aligned AlGaN/GaN high electron mobility trasistors (HEMTs) employing Ir/Pt/Au or Ni/Au gate and non-alloyed ohmic contact metallizations.
Download or read book State of the Art Program on Compound Semiconductors 45 SOTAPOCS 45 and Wide Bandgap Semiconductor Materials and Devices 7 written by F. Ren and published by The Electrochemical Society. This book was released on 2006 with total page 491 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains papers from two symposia: State of the Art Program on Compound Semiconductors 45 and Wide Bandgap Semiconductor Materials and Devices VII.
Download or read book High Temperature Stable W and WSi3 Ohmic Contacts on GaN and InGaN written by and published by . This book was released on 1996 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: Conventional III-V metallizations chemes such as Au/Ge/Ni, Ti/Pt/Au, and Au/Be were found to display poor thermal stability on both GaN and InGaN, with extensive reaction and contact degradation at ≤500 C. By contrast, W was found to produce low contact resistance (?{sub c}-8x10−5?cm2) to n-GaN. Ga outdiffusion to the surface of thin (500 A) W films was found after annealing at 1,100 C, but not at 1000 C. Interfacial abruptness increased by 300A after 1,100 C annealing. In the case of WSi{sub X} (X=0.45), Ga outdiffusion was absent even at 1,100 C, but again there was interfacial broadening and some phase changes in the WSi{sub X}. On In{sub 0.5}Ga{sub 0.5}N, a minimum specific contact resistivity of 1.5 x10−5?cm2 was obtained for WSi{sub X} annealed at 700 C. These contacts retained a smooth morphology and abrupt interfaces to 800 C. Graded In{sub X}Ga{sub 1-X}N layers have been employed on GaAs/AlGaAs HBTs (heterojunction bipolar transistors), replacing conventional In{sub X}Ga{sub 1-X}As layers. R{sub C} values of 5x10−7?cm2 were obtained for nonalloyed Ti/Pt/Au on the InGaN, and the morphologies were superior to those of InGaAs contact layers. This proves to have significant advantages for fabrication of sub-micron HBTs. Devices with emitter dimensions of 2x5?m2 displayed gains of 35 for a base doping level of 7x1019cm−3 and stable long-term behavior.
Download or read book An Analysis of Metal Contacts to GaN written by William Patrick Lewis and published by . This book was released on 2007 with total page 149 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ohmic and Schottky contacts to GaN on sapphire and free standing GaN are investigated. A detailed analysis of the circular Transmission Line Mea-surement (c-TLM) technique is carried out. We show the need to accurately measure the contact radii to extract accurate contact resistivity values, _c using c-TLM, for contacts to p-type GaN. Small measurement errors, _ 0.5 _m, lead to large errors in _c, especially as _c decreases. An alternative technique to extract _c, based on the series resistance of a p-n diode, is investigated. This method relies on uniform current density over the whole metal{semiconductor diode contact and the existence of a singular diode ideality. Defects in p-type GaN on LED material are shown to electroplate preferentially. Ni plated defects annealed in an O2 atmosphere are shown to be passivated, with signi_cant measured improvements in the I{V and L{I char- acteristics of LEDs. Electroless deposition is explored as an alternative contact formation technique. This novel approach yields Ni/Au, p-type ohmic contacts, with a _c comparable with evaporated contacts. A _c of 2.2 x 10_2 cm_2 at room temperature and a _c of 2.5 x 10_2 cm_2 at 410 K indicate the tunneling nature of the contact. The method provides for a reduction in the cost and processing time associated with ohmic contact formation. CoW contacts to n-type GaN are shown to be rectifying even after a 6500C anneal. KOH etching of Ga-face, freestanding, n-type, GaN, is shown to aid ohmic contact formation and remove the need for a high temperature anneal. Schottky contacts were optimised on low doped epi-layers, on free standing n-GaN substrates. The contacts are governed by thermionic emission, with low ideality, 1.04 and low on-state resistance, 0.57 mcm2. The idealities of the devices are shown to decrease with increasing temperature, while the barrier heights remain relatively constant. KOH treatments of the material were shown to increase the Schottky barrier height and reduce reverse leakage currents.
Download or read book High Temperature Stable W and WSi sub X Ohmic Contacts on GaN and InGaN written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Conventional III-V metallizations chemes such as Au/Ge/Ni, Ti/Pt/Au, and Au/Be were found to display poor thermal stability on both GaN and InGaN, with extensive reaction and contact degradation at[le]500 C. By contrast, W was found to produce low contact resistance ([rho][sub c][similar-to]8x10[sup -5][Omega]cm[sup 2]) to n-GaN. Ga outdiffusion to the surface of thin (500 A) W films was found after annealing at 1,100 C, but not at 1000 C. Interfacial abruptness increased by 300A after 1,100 C annealing. In the case of WSi[sub X] (X=0.45), Ga outdiffusion was absent even at 1,100 C, but again there was interfacial broadening and some phase changes in the WSi[sub X]. On In[sub 0.5]Ga[sub 0.5]N, a minimum specific contact resistivity of 1.5 x10[sup -5][Omega]cm[sup 2] was obtained for WSi[sub X] annealed at 700 C. These contacts retained a smooth morphology and abrupt interfaces to 800 C. Graded In[sub X]Ga[sub 1-X]N layers have been employed on GaAs/AlGaAs HBTs (heterojunction bipolar transistors), replacing conventional In[sub X]Ga[sub 1-X]As layers. R[sub C] values of 5x10[sup -7][Omega]cm[sup 2] were obtained for nonalloyed Ti/Pt/Au on the InGaN, and the morphologies were superior to those of InGaAs contact layers. This proves to have significant advantages for fabrication of sub-micron HBTs. Devices with emitter dimensions of 2x5[mu]m[sup 2] displayed gains of 35 for a base doping level of 7x10[sup 19]cm[sup -3] and stable long-term behavior.
Download or read book Thermally Stable Metal GaAs Contacts written by Jian Ding and published by . This book was released on 1989 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Metal Contacts on ZnSe and GaN written by Kristen Joy Duxstad and published by . This book was released on 1997 with total page 380 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Gallium Nitride Processing for Electronics Sensors and Spintronics written by Stephen J. Pearton and published by Springer Science & Business Media. This book was released on 2006-02-24 with total page 402 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiconductor spintronics is expected to lead to a new generation of transistors, lasers and integrated magnetic sensors that can be used to create ultra-low power, high speed memory, logic and photonic devices. Useful spintronic devices will need materials with practical magnetic ordering temperatures and current research points to gallium and aluminium nitride magnetic superconductors as having great potential. This book details current research into the properties of III-nitride semiconductors and their usefulness in novel devices such as spin-polarized light emitters, spin field effect transistors, integrated sensors and high temperature electronics. Written by three leading researchers in nitride semiconductors, the book provides an excellent introduction to gallium nitride technology and will be of interest to all reseachers and industrial practitioners wishing to keep up to date with developments that may lead to the next generation of transistors, lasers and integrated magnetic sensors.
Download or read book State of the Art Program on Compound Semiconductors 46 SOTAPOCS 46 and Processes at the Semiconductor Solution Interface 2 written by C. O'Dwyer and published by The Electrochemical Society. This book was released on 2007 with total page 647 pages. Available in PDF, EPUB and Kindle. Book excerpt: Section 1 addresses the most recent developments in processes at the semiconductor-solution interface include etching, oxidation, passivation, film growth, porous semiconductor formation, electrochemical, photoelectrochemical, electroluminescence and photoluminescence processes, electroanalytical measurements and related topics on both elemental and compound semiconductors. Section 2 addresses the most recent developments in compound semiconductors encompassing advanced devices, materials growth, characterization, processing, device fabrication, reliability, and related topics.
