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1.
The effect of nanoscale patterning using a self-organized porous anodic alumina (PAA) mask on the electrical properties of
ohmic and Schottky contacts to n-GaN was investigated with the aim of evaluating this approach as a method for reducing the
specific contact resistance of ohmic contacts to GaN. The electrical characteristics of contacts to these nanopatterned GaN
samples were compared with contacts to planar, chemically prepared (“as-grown”) GaN samples and reactive ion etched (RIE)
GaN films without any patterning. The specific contact resistivities to unintentionally doped n-GaN using a Ti/Al bilayer
metallization were determined to be 7.4 × 10−3 Ω cm2 for the RIE sample and 7.0 × 10−4 Ω cm2 for the PAA patterned sample. Schottky metal contacts with Pt and Ni were prepared on the three samples to validate the effects
of RIE and nanopatterning on electrical behavior. The effective barrier height was decreased and the reverse current was increased
significantly in the PAA patterned sample. The radius of curvature of the nanoscale corrugation in the patterned interface
was smaller than the depletion width. The reduction of the depletion width at sharp corners enhanced the local tunneling current,
reducing the specific contact resistivity and decreasing the effective barrier height. These results suggest that nanopatterning
with PAA on GaN can significantly lower the contact resistance. 相似文献
2.
M. T. Hirsch K. J. Duxstad E. E. Haller S. Ruvimov Z. Liliental-Weber 《Journal of Electronic Materials》1998,27(11):1236-1239
We correlate structural and electrical characteristics of as-deposited and low-temperature annealed Ti contacts on GaN. Temperature
dependent currentvoltage measurements are used to determine the effective barrier heights of the respective contacts, while
high-resolution transmission electron microscopy is utilized for structural characterization. As-deposited Ti contacts are
slightly rectifying with an effective barrier height of ∼200 meV. After annealing at 230°C, the barrier height increases to
values of ∼450 meV. A similar behavior of Schottky contacts with more strongly rectifying diodes upon low-temperature annealing
is observed for Zr metal contacts on GaN. As-deposited Ti already forms a thin TiN layer at the GaN interface. After annealing
at 230°C, the average thickness and the distribution of TiN grains remain practically unchanged, but the interface with GaN
roughens. We correlate the observed barrier height changes with interface roughness and phase formation and we discuss the
results in terms of interface damage and the Schottky-Mott theory. 相似文献
3.
Ippei Fujimoto Hirokuni Asamizu Masahiro Shimada Miki Moriyama Naoki Shibata Masanori Murakami 《Journal of Electronic Materials》2003,32(9):957-963
To understand formation and deterioration mechanisms of Ta/Ti ohmic contacts that were previously developed for p-GaN, the
electrical properties of the Ta/Ti contacts, which were deposited on undoped GaN substrates and subsequently annealed in vacuum
(where a slash (/) sign indicates the deposition sequence), were studied. The Ta/Ti contacts displayed good ohmic behavior
after annealing at a temperature of 800°C for 10 min in vacuum, although the undoped GaN substrates were used. However, deterioration
of the present ohmic contacts was observed during room-temperature storage. These contact properties were similar to those
observed in the Ta/Ti contacts prepared on p-GaN. Hall-effect measurements revealed that thin n-type conductive layers were
found to form on surfaces of both the undoped GaN and p-GaN substrates after annealing at 800°C in vacuum. 相似文献
4.
In this study, the current density-voltage (J-V) characteristic of Schottky diodes of indium-tin-oxide (ITO) contacts to p-type
GaN (p-GaN) has been investigated. The calculated barrier-height value of ITO/p-GaN samples using the thermionic field-emission
(TFE) model is 3.2 eV, which implies that the work function of ITO is equal to 4.3 eV. The result is supported by J-V measurements
of ITO/n-type GaN Schottky diodes. On the other hand, the barrier height of ITO/p-GaN was also determined from x-ray photoelectron
spectroscopy (XPS) data. The analysis of the XPS spectral shifts indicated that this observed barrier-height value of ITO/p-GaN
by XPS is in good agreement with the value of 3.2 eV obtained from J-V measurements. 相似文献
5.
Recently, Au/Ni/p-type GaN ohmic contacts annealed in an air ambient have been widely investigated. However, to obtain a low
specific-contact resistance, the annealing window is limited. In this study, to understand the oxidation function of metallic
Ni, the Au/Ni/p-type GaN structure was annealed in an air ambient for 10 min at various temperatures. Using x-ray photoelectron
spectroscopy (XPS) analysis, the metallic Ni was oxidized into NiO and NiO1.3 compositions at annealing temperatures of 500°C and 600°C, respectively. However, metallic Ni still existed on the interface
of the Ni/p-type GaN annealed at 400°C. The associated barrier heights of 0.42 eV, 0.21 eV, and 0.31 eV were obtained with
p-type GaN for the Ni, NiO, and NiO1.3 contacts, respectively. The hole concentrations of p-type NiO and p-type NiO1.3 were 2.6×1016 cm−3 and 2.0×1018 cm−3, respectively. The lower hole concentration of the p-type NiO would lead to reducing the valence-band bending of the p-type
GaN, as well as the barrier height for holes crossing from the p-type NiO to the p-type GaN. The formation of NiO was thus
an important issue for lowering the specific-contact resistance of the Au/Ni/p-type GaN ohmic contacts annealed in an air
ambient. 相似文献
6.
Metal contacts to n-type GaN 总被引:4,自引:0,他引:4
A. C. Schmitz A. T. Ping M. Asif Khan Q. Chen J. W. Yang I. Adesida 《Journal of Electronic Materials》1998,27(4):255-260
Contacts consisting of various single layer metals to n-type GaN have been formed and characterized. The current-voltage characteristics
were measured for 17 different metals (Sc, Hf, Zr, Ag, Al, V, Nb, Ti, Cr, W, Mo, Cu, Co, Au, Pd, Ni, and Pt) deposited on
the same epitaxial growth layer. The barrier height, ideality factor, breakdown voltage, and effective Richardson coefficients
were measured from those metals which exhibited strong rectifying behavior. The barrier heights for these metal contacts were
measured using current-voltage-temperature and capacitance-voltage techniques. It was found that an increase in metal work
function correlated with an increase in the barrier height. The surface state density of GaN was approximated to be very similar
to CdS and almost a factor of ten less than GaAs. 相似文献
7.
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
8.
Calculations of specific contact resistance as a function of doping and barrier height were performed for p-type GaN. These
calculations took into account two valence bands, each with different effective masses, and show that at low doping, the heavy
hole band accounts for most of the conduction, whereas at heavier doping, the light hole band dominates conduction. These
calculations also indicate the barrier height for typical contacts to p-GaN is between 0.75 eV and 1 eV. Specific contact
resistance measurements were made for oxidized Ni/Au, Pd, and oxidized Ni/Pd ohmic contact metal schemes to p-GaN. The Ni/Pd
contact had the lowest specific contact resistance, 6×10−4 Ω cm2. Auger sputter depth profile analysis showed some Ni diffused away from the GaN surface to the contact surface with the bulk
of the Pd located in between two areas of Ni. Both Ni and Pd interdiffused with the GaN at the semiconductor surface. The
majority of the oxygen observed was with the Ni as NiO. Angle-resolved-x-ray photoelectron spectroscopy (AR-XPS) analyses
showed the formation of predominantly NiO and PdO species, with higher Ni and Pd oxides at the contact surface. 相似文献
9.
Mechanisms of current flow in metal-semiconductor ohmic contacts 总被引:1,自引:0,他引:1
Published data on the properties of metal-semiconductor ohmic contacts and mechanisms of current flow in these contacts (thermionic emission, field emission, thermal-field emission, and also current flow through metal shunts) are reviewed. Theoretical dependences of the resistance of an ohmic contact on temperature and the charge-carrier concentration in a semiconductor were compared with experimental data on ohmic contacts to II–VI semiconductors (ZnSe, ZnO), III–V semiconductors (GaN, AlN, InN, GaAs, GaP, InP), Group IV semiconductors (SiC, diamond), and alloys of these semiconductors. In ohmic contacts based on lightly doped semiconductors, the main mechanism of current flow is thermionic emission with the metal-semiconductor potential barrier height equal to 0.1–0.2 eV. In ohmic contacts based on heavily doped semiconductors, the current flow is effected owing to the field emission, while the metal-semiconductor potential barrier height is equal to 0.3–0.5 eV. In alloyed In contacts to GaP and GaN, a mechanism of current flow that is not characteristic of Schottky diodes (current flow through metal shunts formed by deposition of metal atoms onto dislocations or other imperfections in semiconductors) is observed. 相似文献
10.
研究了调制掺杂 Alx Ga1 - x N/Ga N表面 Pt肖特基接触的制备工艺 ,并对其进行了 I-V测量。通过改变对样品表面的处理工艺 ,研究了表面处理对调制掺杂 Alx Ga1 - x N/Ga N表面 Pt肖特基结接触特性的影响 ,在 n型掺杂浓度为 7.5× 1 0 1 7cm- 3的 Al0 .2 2 Ga0 .78N样品表面 ,制备得到了势垒高度为 0 .94e V、理想因子为 1 .4的 Pt肖特基接触。这与国外报道的结果接近 (=1 .2 e V,n=1 .1 1 [1 ] ) 相似文献
11.
Rongming Chu Likun Shen Fichtenbaum N. Brown D. Keller S. Mishra U.K. 《Electron Device Letters, IEEE》2008,29(4):297-299
It has been found that the reverse leakage current of AlGaN/GaN Schottky contacts can be significantly reduced by a CF4 plasma treatment prior to the Schottky metal evaporation. The data of electrical characterization suggest that the leakage reduction is related to the modification of the semiconductor surface by plasma treatment. The leakage reduction effect was also observed in GaN Schottky contacts. Capacitance-voltage characterization of the GaN Schottky contacts indicates that the Schottky barrier height was slightly increased by the plasma treatment. A two-step surface treatment procedure, consisting of a BCI3 plasma treatment followed by a brief CF4 plasma treatment, has been developed as an efficient approach to reduce the reverse leakage of the Schottky contacts, while avoiding side effects related to the CF4 plasma. 相似文献
12.
13.
采用光调制反射光谱(PR)研究了(0001)晶向蓝宝石村底上MOCVD方法生长的单晶六角GaN薄膜的室温光学性质。测得六角GaN薄膜的禁带宽度为3.400eV,对PR谱的调制机理进行了分析,发现信号来自缺陷作用下的表面电场调制。光吸收增和光反射谱的测量,得到3.39eV的光学吸收边和3.3eV的反射峰,证实了光调制反射光谱的结果。 相似文献
14.
15.
Using the measured capacitance–voltage and current–voltage characteristics of the rectangular Al N/Ga N heterostructure field-effect transistors(HFETs) with the side-Ohmic contacts, it was found that the polarization Coulomb field scattering in the Al N/Ga N HFETs was greatly weakened after the side-Ohmic contact processing, however, it still could not be ignored. It was also found that, with side-Ohmic contacts, the polarization Coulomb field scattering was much stronger in Al N/Ga N HFETs than in Al Ga N/Al N/Ga N and In0:17Al0:83N/Al N/Ga N HFETs, which was attributed to the extremely thinner barrier layer and the stronger polarization of the Al N/Ga N heterostructure. 相似文献
16.
基于凹槽栅增强型氮化镓高电子迁移率晶体管(GaN HEMT)研究了不同的栅槽刻蚀工艺对GaN器件性能的影响。在栅槽刻蚀方面,采用了一种感应耦合等离子体(ICP)干法刻蚀技术与高温热氧化湿法刻蚀技术相结合的两步法刻蚀技术,将AlGaN势垒层全部刻蚀掉,制备出了阈值电压超过3 V的增强型Al_2O_3/AlGaN/GaN MIS-HEMT器件。相比于传统的ICP干法刻蚀技术,两步法是一种低损伤的自停止刻蚀技术,易于控制且具有高度可重复性,能够获得更高质量的刻蚀界面,所制备的器件增强型GaN MIS-HEMT器件具有阈值电压回滞小、电流开关比(ION/IOFF)高、栅极泄漏电流小、击穿电压高等特性。 相似文献
17.
基于Sentaurus Workbench(SWB)TCAD可制造性设计平台进行AlGaN/GaN器件的结构设计和仿真,并对影响二维电子气的重要参数因素进行了研究及优化,诸如AlGaN势垒层中Al组分x、AlGaN势垒层厚度h、应变弛豫度r和栅偏压Vg等因素。参数相关性的制约结果,无疑会反映在对器件物理特性的制约及影响上。研究结果表明,在一定条件下增大势垒层中Al组分和势垒层厚度可以提高器件的电流传输特性。然而随着二者的不断增大将会引起应变弛豫的发生,而应变弛豫的发生会降低器件的性能。 相似文献
18.
T. V. L’vova V. L. Berkovits M. S. Dunaevskii V. M. Lantratov I. V. Makarenko V. P. Ulin 《Semiconductors》2003,37(8):931-935
The influence exerted by wet chemical nitridation of the (100)GaAs substrate surface in hydrazinesulfide solutions before
fabrication of barrier contacts on the parameters of surface-barrier Au-Ti/GaAs structures has been studied. The structures
fabricated on nitrided substrates are characterized by lower reverse currents and higher breakdown voltages. The barrier height
in structures of this kind is 0.71±0.02 eV, and the ideality factor, 1.06±0.01. The observed improvement in the electrical
parameters of the structures is due to replacement of the natural oxide layer on the substrate surface by a thin coherent
GaN film. 相似文献
19.
A. Kurtenbach C. Ulrich N. Y. Jin-Phillipp F. Noll K. Eberl K. Syassen F. Phillipp 《Journal of Electronic Materials》1996,25(3):395-400
We report on the growth of InP/GalnP islands on GaAs substrates by solidsource molecular beam epitaxy. It is shown by reflection
high energy electron diffraction and atomic force microscopy that a rapid change from a twodimensional to a three-dimensional
growth mode occurs at about nominally 1.5 monolayers (MLs) InP. Transmission electron microscopy measurements demonstrate
the coherent incorporation of InP islands in an GalnP matrix for nominally 2.5 MLs InP. The energy of the InP photoluminescence
(PL) shifts to lower energies (100 meV) when the growth interruption time between the island and cap layer growth is increased
from 1 to 300 s in case of nominally 3 MLs InP. Simultaneously, an increase of the PL linewidth is observed from 30 to 60
meV. Room temperature photoreflectance measurements on samples with various InP thickness have been performed. Compared to
PL measurements, an additional feature in the photoreflectance spectra is observed for samples with more than 7 MLs InP, which
is attributed to a transition between excited electron and hole states of the islands. 相似文献
20.
《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