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161.
162.
The effect of reactive ion etch (RIE) induced damage on 4H-SiC surfaces etched in fluorinated plamas has been investigated
and characterized using Ni Schottky diodes and x-ray photoelectron spectroscopic surface analysis. The diodes were characterized
using current-voltage, current-voltage-temperature, and capacitance-voltage measurements with near ideal forward characteristics
(n=1.07) and forward current density as high as 9000 A/cm2 from the control (unetched) devices. High current handling capability was observed in diodes with etched surfaces as well.
Diodes with surfaces etched in CHF3 containing plasmas showed a significant reduction in the barrier height compared to the diodes with surfaces etched in CF4 containing plasma. Control devices exhibited high leakages when reverse biased, which is attributed to the presence of a
thin (∼2 nm) oxide layer at the metal-semiconductor interface. However, under reverse bias diodes with CHF3-etched surfaces showed improvement in leakage current compared to diodes with CF4-etched surfaces and the control diodes. 相似文献
163.
B. P. Luther S. E. Mohney J. M. Delucca R. F. Karlicek Jr. 《Journal of Electronic Materials》1998,27(4):196-199
The annealing conditions and contact resistivities of Ta/Al ohmic contacts to n-type GaN are reported for the first time.
The high temperature stability and mechanical integrity of Ti/Al and Ta/Al contacts have been investigated. Ta/Al (35 nm/115
nm) contacts to n-type GaN became ohmic after annealing for 3 min at 500°C or for 15 s at 600°C. A minimum contact resistivity
of 5×10−6Ω cm2 was measured after contacts were repatterned with an Al layer to reduce the effect of a high metal sheet resistance. Ti/Al
and Ta/Al contacts encapsulated under vacuum in quartz tubes showed a significant increase in contact resistivity after aging
for five days at 600°C. Cross section transmission electron microscopy micrographs and electrical measurements of aged samples
indicate that the increased contact resistivity is primarily the result of degradation of the metal layers. Minimal reactions
at the metal/GaN interface of aged samples were observed. 相似文献
164.
M. K. Rabinal I. Lyubomirsky E. Pekarskaya V. Lyakhovitskaya David Cahen 《Journal of Electronic Materials》1997,26(8):893-897
Room temperature formation of ohmic contacts by electroplating gold on chemically treated surfaces of p-CuInSe2 and p-CdTe single crystals is reported. The effect of Br2/methanol and KOH+KCN+H2O treatments prior to plating was analyzed in the case of CuInSe2. It is shown that the former treatment yields better ohmic contacts, with lower contact resistance, than the latter. While
annealing these contacts made them highly non-ohmic, the method gives reasonably ohmic contacts on surfaces, that were purposely
oxidized prior to contact preparation. In the case of p-CdTe stable, low resistance ohmic contacts were obtained at room temperature by electrochemical diffusion of Hg from solution, prior to gold plating. The treatment forms a highly degenerated p+- HgCdTe layer. The contacts, which have a very low contact to bulk resistivity ratio, were further improved by vacuum annealing. 相似文献
165.
Au/n-GaN Schottky diodes with the Au electrode deposited at low temperature (LT=77K) have been studied. In comparison, the
same chip of GaN epitaxial layer was also used for room temperature Schottky diodes. The low temperature Schottky diodes exhibit
excellent performance. Leakage current density as low as 2.55×10−11 A·cm−2 at −2.5 V was obtained in the LT Schottky diodes. The linear region in the current-voltage curve at forward bias extends
more than eight orders in current magnitude. Current-voltage-temperature measurements were carried out to study the characteristics
of the LT Schottky diodes. A typical barrier height of about 1.32 eV for the LT diode, which is the highest value ever reported,
was obtained. The obvious enhancement in electrical performance makes the LT processing a very promising technique for GaN
device application although the detailed mechanisms for the LT Au/n-GaN Schottky diodes are still under investigation. 相似文献
166.
本文对一些毫米波肖特基势混频二极管本征噪声温度进行了测试和分析。介绍了在常温和致冷下混频二极管本征噪声的测试方法。 相似文献
167.
Current transport in molecular beam epitaxy (MBE) GaAs grown at low and intermediate growth temperatures is strongly affected
by defects. A model is developed here that shows that tunneling assisted by defect states can dominate, at some bias ranges,
current transport in Schottky contacts to unannealed GaAs material grown at the intermediate temperature range of about 400°C.
The deep defect states are modeled by quantum wells which trap electrons emitted from the cathode before re-emission to semiconductor.
Comparison of theory with experimental data shows defect states of energies about 0.5 eVbelow conduction band to provide the
best fit to data. This suggests that arsenic interstitials are likely to mediate this conduction. Comparison is also made
between as-grown material and GaAs grown at the same temperature but annealed at 600°C. It is suggested that reduction of
these defects by thermal annealing can explain lower current conduction at high biases in the annealed device as well as higher
current conduction at low biases due to higher lifetime. Quenching of current by light in the as-grown material can also be
explained based on occupancy of trap states. Identification of this mechanism can lead to its utilization in making ohmic
contacts, or its elimination by growing tunneling barrier layers. 相似文献
168.
D. Selvanathan L. Zhou V. Kumar I. Adesida N. Finnegan 《Journal of Electronic Materials》2003,32(5):335-340
Improved performance of the ohmic contacts on n-GaN has been demonstrated with the use of MoAu as the capping layer on TiAl
metallization. Contact resistance as low as 0.13 Θ-mm was achieved in these ohmic contacts when annealed at 850°C for 30 sec.
We have studied the long-term thermal stability of these contacts at 500°C, 600°C, 750°C, and 850°C, respectively. The Ti/Al/Mo/Au
metallization forms low contact-resistance ohmic contacts on n-GaN that are stable at 500°C and 600°C after 25 h of thermal
treatment. The ohmic-contact performance degrades after 10 h of thermal treatment at 750°C, while the contacts exhibit nonlinear
current-voltage (I-V) characteristics after 1 h of thermal treatment at 850°C with the formation of oxide on the surface of
the contacts accompanied by surface discoloration. The intermetallic reactions taking place in the contacts during the long-term
thermal treatments were studied using Auger electron spectroscopy (AES), and the surface morphology was characterized using
atomic force microscopy (AFM). 相似文献
169.
Using an ab initio total energy approach, we study the electronic structure of metal/MgO(100) interfaces. By considering simple and transition metals, different adsorption sites and different interface separations, we analyze the influence of the character of metal and of the detailed interfacial atomic structure. We calculate the interface density of states, electron transfer, electric dipole, and the Schottky barrier height. We characterize three types of electronic states: states due to chemical bonding which appear at well defined energies, conventional metal-induced gap states associated to a smooth density of states in the MgO gap region, and metal band distortions due to polarization by the electrostatic field of the ionic substrate. We point out that, with respect to the extended Schottky limit, the interface formation yields an electric dipole mainly determined by the substrate characteristics. Indeed, the metal-dependent contributions (interfacial states and electron transfer) remain small with respect to the metal polarization induced by the substrate electrostatic field. 相似文献
170.
The defects induced by inductively coupled plasma reactive ion etching (ICP-RIE) on a Si-doped gallium nitride (GaN:Si) surface have been analyzed. According to the capacitance analysis, the interfacial states density after the ICP-etching process may be higher than 5.4 × 1012 eV−1 cm−2, compared to around 1.5 × 1011 eV−1 cm−2 of non-ICP-treated samples. After the ICP-etching process, three kinds of interfacial states density are observed and characterized at different annealing parameters. After the annealing process, the ICP-induced defects could be reduced more than one order of magnitude in both N2 and H2 ambient. The H2 ambient shows a better behavior in removing ICP-induced defects at a temperature around 500 °C, and the interfacial states density around 2.2 × 1011 eV−1 cm−2can be achieved. At a temperature higher than 600 °C, the N2 ambient provides a much more stable interfacial states behavior than the H2 ambient. 相似文献