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1.
Mulpuri V. Rao Sadanand M. Gulwadi Phillip E. Thompson Ayub Fathimulla Olaleye A. Aina 《Journal of Electronic Materials》1989,18(2):131-136
Halogen lamp rapid thermal annealing was used to activate 100 keV Si and 50 keV Be implants in In0.53Ga0.47As for doses ranging between 5 × 1012−4 × 1014 cm−2. Anneals were performed at different temperatures and time durations. Close to one hundred percent activation was obtained
for the 4.1 × 1013 cm−2 Si-implant, using an 850° C/5 s anneal. Si in-diffusion was not observed for the rapid thermal annealing temperatures and
times used in this study. For the 5 × 1013 cm−2 Be-implant, a maximum activation of 56% was measured. Be-implant depth profiles matched closely with gaussian profiles predicted
by LSS theory for the 800° C/5 s anneals. Peak carrier concentrations of 1.7 × 1019 and 4 × 1018 cm−3 were achieved for the 4 × 1014 cm−2 Si and Be implants, respectively. For comparison, furnace anneals were also performed for all doses. 相似文献
2.
K.K. Allums M. Hlad A.P. Gerger B.P. Gila C.R. Abernathy S.J. Pearton F. Ren R. Dwivedi T.N. Fogarty R. Wilkins 《Journal of Electronic Materials》2007,36(4):519-523
Proton irradiation of Sc2O3/GaN and Sc2O3/MgO/GaN metal-oxide semiconductor diodes was performed at two energies, 10 MeV and 40 MeV, and total fluences of 5 × 109 cm−2, corresponding to 10 years in low-earth orbit. The proton damage causes a decrease in forward breakdown voltage and a flat-band
voltage shift in the capacitance-voltage characteristics, indicating a change in fixed oxide charge and damage to the dielectric.
The interface state densities after irradiation increased from 5.9 × 1011 cm−2 to 1.03 × 1012 cm−2 in Sc2O3/GaN diodes and from 2.33 × 1011 to 5.3 × 1011 cm−2 in Sc2O3/MgO/GaN diodes. Postannealing at 400°C in forming gas recovered most of the original characteristics but did increase the
interfacial roughness. 相似文献
3.
Jong Kyu Kim Jung Ho Je Jae Won Lee Yong Jo Park Taeil Kim In-Ok Jung Byung-Teak Lee Jong-Lam Lee 《Journal of Electronic Materials》2001,30(2):L8-L12
Electrical properties of Ni/Au ohmic contacts on p-type GaN were interpreted with the change of microstructure observed under
transmission electron microscopy. The contact resistivity was decreased from 1.3×10−2 to 6.1×10−4 Ωcm2 after annealing at 600°C. The reduction is due to the dissolution of Ga atoms into Au−Ni solid solution formed during annealing,
via the generation of Ga vacancies. Thus, net concentration of holes increased below the contact, resulting in the reduction
of contact resistivity. At 800°C, N atoms decomposed; reacted with Ni, and forming cubic Ni4N. Consequently, N vacancies, acting as donors in GaN, were generated below the contact, leading to the increase of contact
resistivity to 3.8×10−2 Ωcm2. 相似文献
4.
M. A. Sánchez-García E. Calleja F. J. Sanchez F. Calle E. Monroy D. Basak E. Muñoz C. Villar A. Sanz-Hervas M. Aguilar J. J. Serrano J. M. Blanco 《Journal of Electronic Materials》1998,27(4):276-281
GaN layers have been grown by plasma-assisted molecular beam epitaxy on AlN-buffered Si(111) substrates. An initial Al coverage
of the Si substrate of aproximately 3 nm lead to the best AlN layers in terms of x-ray diffraction data, with values of full-width
at half-maximum down to 10 arcmin. A (2×2) surface reconstruction of the AlN layer can be observed when growing under stoichiometry
conditions and for substrate temperatures up to 850°C. Atomic force microscopy reveals that an optimal roughness of 4.6 nm
is obtained for AlN layers grown at 850°C. Optimization in the subsequent growth of the GaN determined that a reduced growth
rate at the beginning of the growth favors the coalescence of the grains on the surface and improves the optical quality of
the film. Following this procedure, an optimum x-ray full-width at half-maximum value of 8.5 arcmin for the GaN layer was
obtained. Si-doped GaN layers were grown with doping concentrations up to 1.7×1019 cm−3 and mobilities approximately 100 cm2/V s. Secondary ion mass spectroscopy measurements of Be-doped GaN films indicate that Be is incorporated in the film covering
more than two orders of magnitude by increasing the Be-cell temperature. Optical activation energy of Be acceptors between
90 and 100 meV was derived from photoluminescence experiments. 相似文献
5.
Ching-Ting Lee Ming-Yuan Yeh Chang-Da Tsai Yen-Tang Lyu 《Journal of Electronic Materials》1997,26(3):262-265
A bilayer Nd/Al metallization structure has been deposited onto low pressure organometallic vapor phase epitaxy grown n-type
GaN ( 1 × 1018 cm−3) by electron-beam evaporation. Ohmic metal contacts were patterned photolithographically for standard transmission line measurement,
and then thermally annealed at temperatures ranging from 200 to 350°C and from 500 to 650°C using conventional thermal annealing
(CTA) and rapid thermal annealing (RTA), respectively. The lowest values for the specify contact resistivity of 9.8 × 10−6 Ω−cm2 and 8 × 10−6 Ω−cm2 were obtained using Nd/Al metallization with CTA of 250°C for 5 min and RTA of 600°C for 30 s. Examination of the surface
morphology using atomic force microscopy as a function of annealing temperature revealed that the surface roughness was strongly
influenced by conventional thermal annealing, it was smooth in the temperature range from 550 to 650°C for rapid thermal annealing.
Auger electron spectroscopy depth profiling was employed to investigate the metallurgy and interdiffusion of contact formation. 相似文献
6.
E. Dimakis E. Iliopoulos M. Kayambaki K. Tsagaraki A. Kostopoulos G. Konstantinidis A. Georgakilas 《Journal of Electronic Materials》2007,36(4):373-378
The molecular beam epitaxy of In-face InN (0001) epilayers with optimized surface morphology, structural quality, and electrical
properties was investigated. Namely, compact InN epilayers with atomically flat surfaces, grown in a step-flow mode, were
obtained using stoichiometric fluxes of In and N and substrate temperatures in the range from 400°C to 435°C. Typical values
for the electron concentration and the Hall mobility at 300 K were 4.3 × 1018 cm−3 and 1210 cm2/Vs, respectively. The growth mode of InN during the very first stage of the nucleation was investigated analytically, and
it was found that the growth proceeds through nucleation and fast coalescence of two-dimensional (2-D)–like InN islands. The
preceding conditions were used to grow an InN/GaN quantum well (QW) heterostructure, which exhibited well-defined interfaces.
Schottky contacts were successfully fabricated using a 15-nm GaN barrier enhancement cap layer. Capacitance-voltage measurements
revealed the confinement of electrons within the InN QW and demonstrated the capability to modulate the electron density within
an InN channel. The sheet concentration of the confined electrons (1.5 × 1013 cm−2) is similar to the calculated sheet polarization charge concentration (1.3 × 1013 cm−2) at the InN/GaN interface. However, electrons may also originate from ionized donors with a density of 8 × 1018 cm−3 within the InN layer. 相似文献
7.
Nadeemullah Mahadik Mulpuri V. Rao Albert V. Davydov 《Journal of Electronic Materials》2006,35(11):2035-2040
The performance of a novel Ge/Cu/Ti metallization scheme on n-type GaN has been investigated for obtaining thermally and electrically
stable low-resistance ohmic contacts. Isochronal (2 min.) anneals in the 600–740°C temperature range and isothermal (690°C)
anneals for 2–10 min. duration were performed in inert atmosphere. For the 690°C isothermal schedule, ohmic behavior was observed
after annealing for 3 min. or longer with a lowest contact resistivity of 9.1 × 10−5 Ωcm2 after the 10 min. anneal for a net donor doping concentration of 9.2 × 1017 cm−Ω3. Mean roughness (Ra) for anneals at 690°C was almost constant at around 5 nm, up to an annealing duration of 10 min., which indicates a good
thermal stability of the contact scheme. 相似文献
8.
Hwe Jae Lee Soon Jae Yu Hajime Asahi Shun-Ichi Gonda Young Hwan Kim Jin Koo Rhee S. J. Noh 《Journal of Electronic Materials》1998,27(7):829-832
Ohmic contacts with low resistance are fabricated on n-GaN films using Al/Ti bilayer metallization. GaN films used are 0.3
μm thick layers with carrier concentrations of 1 × 1019 cm−3 grown on the c-plane sapphire by ion-removed electron cyclotron resonance molecular beam epitaxy. The lowest value for the
specific contact resistivity (ρc) of 1.2×10−8 Ω·cm2 was obtained with furnace annealing at 500°C for 60 min. This result shows the effectiveness of high carrier concentration
GaN layers and the low temperature annealing for the realization of low resistance ohmic contacts. Sputtering Auger electron
spectroscopy analysis reveals that Al diffuses into Ti layer and comes into contact with the GaN surface. 相似文献
9.
Chih-Yang Chang Gou-Chung Chi Wei-Ming Wang Li-Chyong Chen Kuei-Hsien Chen F. Ren S. J. Pearton 《Journal of Electronic Materials》2006,35(4):738-743
The transport properties of single GaN and InN nanowires grown by thermal catalytic chemical vapor deposition were measured
as a function of temperature, annealing condition (for GaN) and length/square of radius ratio (for InN). The as-grown GaN
nanowires were insulating and exhibited n-type conductivity (n ≈ 2×1017 cm−3, mobility of 30 cm2/V s) after annealing at 700°C. A simple fabrication process for GaN nanowire field-effect transistors on Si substrates was
employed to measure the temperature dependence of resistance. The transport was dominated by tunneling in these annealed nanowires.
InN nanowires showed resistivity on the order of 4×10−4 Ω cm and the specific contact resistivity for unalloyed Pd/Ti/Pt/Au ohmic contacts was near 1.09×10−7 Ω cm2. For In N nanowires with diameters <100 nm, the total resistance did not increase linearly with length/square of radius ratio
but decreased exponentially, presumably due to more pronounced surface effect. The temperature dependence of resistance showed
a positive temperature coefficient and a functional form characteristic of metallic conduction in the InN nanowires. 相似文献
10.
Yu-Zung Chiou Yan-Kuin Su Shoou-Jinn Chang Jeng Gong Chia-Sheng Chang Sen-Hai Liu 《Journal of Electronic Materials》2003,32(5):395-399
High-quality SiO2 insulating layers were successfully deposited onto GaN by a photo chemical-vapor deposition (photo-CVD) technique using a
deuterium (D2) lamp as the excitation source. The interface-trap density, Dit, was estimated to be 8.4×1011 cm−2eV−1 for the photo-CVD SiO2 layers prepared at 300°C. It was found that the leakage current was only 6.6×10−7 A/cm2 with an applied field of 4 MV/cm for the 300°C photo-CVD-grown Al/SiO2/GaN metal-insulator semiconductor (MIS) capacitor. It was also found that the photo-CVD SiO2 layer could be used to suppress the dark current of nitride-based photodetectors. A large photocurrent to dark-current contrast
ratio higher than three orders of magnitude and a maximum 0.12 A/W responsivity were observed from the fabricated indium tin
oxide (ITO)/photo-SiO2/GaN MIS ultraviolet (UV) photodetectors. Furthermore, it was found that corresponding noise-equivalent power (NEP) and normalized
detectivity, D*, of our ITO/photo-SiO2/GaN MIS UV photodetectors was 2.19×10−9 W and 2.03 × 108 cmHz0.5W−1, respectively, for a given bandwidth of 500 Hz. 相似文献
11.
J. C. Zolper J. Han R. M. Biefeld S. B. van Deusen W. R. Wampler D. J. Reiger S. J. Pearton J. S. Williams H. H. Tan R. F. Karlicek Jr. R. A. Stall 《Journal of Electronic Materials》1998,27(4):179-184
Implant activation annealing of Si-implanted GaN is reported for temperatures from 1100 to 1400°C. Free electron concentrations
up to 3.5×1020 cm−3 are estimated at the peak of the implanted profile with Hall mobilities of ∼60 cm2/Vs for annealing at 1300°C for 30 s with an AIN encapsulant layer. This mobility is comparable to epitaxial GaN doped at
a similarly high level. For annealing at ≥1300°C, the sample must be encapsulated with AIN to prevent decomposition of the
GaN layer. Channeling Rutherford backscattering demonstrates the partial removal of the implant damage after a 1400°C anneal
with a minimum channeling yield of 12.6% compared to 38.6% for the as-implanted spectrum. Scanning electron microscope images
show evidence of decomposition of unencapsulated GaN after a 1300°C anneal and complete sublimation after 1400°C. The use
of AIN encapsulation and annealing at temperatures of ∼1300°C will allow the formation of selective areas of highly doped
GaN to reduce the contact and access resistance in GaN-based transistors and thyristors. 相似文献
12.
E.A. Moore Y.K. Yeo G.J. Gruen Mee-Yi Ryu R.L. Hengehold 《Journal of Electronic Materials》2010,39(1):21-28
Electrical activation studies were carried out on Si-implanted Al0.33Ga0.67N as a function of ion dose, annealing temperature, and annealing time. The samples were implanted at room temperature with
Si ions at 200 keV in doses ranging from 1 × 1014 cm−2 to 1 × 1015 cm−2, and subsequently proximity-cap annealed from 1150°C to 1350°C for 20 min to 60 min in a nitrogen environment. One hundred
percent electrical activation efficiency was obtained for Al0.33Ga0.67N samples implanted with a dose of 1 × 1015 cm−2 after annealing at either 1200°C for 40 min or at 1300°C for 20 min. The samples implanted with doses of 1 × 1014 cm−2 and 5 × 1014 cm−2 exhibited significant activations of 74% and 90% after annealing for 20 min at 1300°C and 1350°C, respectively. The mobility
increased as the annealing temperature increased from 1150°C to 1350°C, showing peak mobilities of 80 cm2/V s, 64 cm2/V s, and 61 cm2/V s for doses of 1 × 1014 cm−2, 5 × 1014 cm−2, and 1 × 1015 cm−2, respectively. Temperature-dependent Hall-effect measurements showed that most of the implanted layers were degenerately
doped. Cathodoluminescence measurements for all samples exhibited a sharp neutral donor-bound exciton peak at 4.08 eV, indicating
excellent recovery of damage caused by ion implantation. 相似文献
13.
R. D. Dupuis C. J. Eiting P. A. Grudowski H. Hsia Z. Tang D. Becher H. Kuo G. E. Stillman M. Feng 《Journal of Electronic Materials》1999,28(3):319-324
Ion implantation into III–V nitride materials is animportant technology for high-power and high-temperature digital and monolithic
microwave integrated circuits. We report the results of the electrical, optical, and surface morphology of Si ion-implanted
GaN films using furnace annealing. We demonstrate high sheet-carrier densities for relatively low-dose (natoms=5×1014 cm−2) Si implants into AlN/GaN/sapphire heteroepitaxial films. The samples that were annealed at 1150°C in N2 for 5 min exhibited a smooth surface morphology and a sheet electron concentration ns ∼9.0×1013 cm−2, corresponding to an estimated 19% electrical activation and a 38% Si donor activation in GaN films grown on sapphire substrates.
Variable-temperature Hall-effect measurem entsindicate a Si donor ionization energy ∼15 meV. 相似文献
14.
The electrical characteristics of both n- and p-type GaN metal-oxide semiconductor (MOS) capacitors utilizing plasma-enhanced
CVD-SiO2 as the gate dielectric were measured. Both capacitance and conductance techniques were used to obtain the MOS properties
(such as interface state density). Devices annealed at 1000°C/30 min. in N2 yielded an interface state density of 3.8×1010 cm−2 eV−1 at 0.19 eV from the conduction band edge, and it decreased to 1.1×1010 cm−2 eV−1 deeper into the band gap. A total fixed oxide charge density of 8×1012 q cm−2 near the valence band was estimated. Unlike the symmetric interface state density distribution in Si, an asymmetric interface
state density distribution with lower density near the conduction band and higher density near the valence band was determined. 相似文献
15.
H. Sheng N. W. Emanetoglu S. Muthukumar B. V. Yakshinskiy S. Feng Y. Lu 《Journal of Electronic Materials》2003,32(9):935-938
Ta/Au ohmic contacts are fabricated on n-type ZnO (∼1 × 1017 cm−3) epilayers, which were grown on R-plane sapphire substrates by metal organic chemical vapor deposition (MOCVD). After growth
and metallization, the samples are annealed at 300°C and 500°C for 30 sec in nitrogen ambient. The specific contact resistance
is measured to be 3.2×10−4 Ωcm2 for the as-deposited samples. It reduces to 5.4×10−6 Ωcm2 after annealing at 300°C for 30 sec without significant surface morphology degradation. When the sample is annealed at 500°C
for 30 sec, the specific contact resistance increases to 3.3 × 10−5 Ωcm2. The layer structures no longer exist due to strong Au and Ta in-diffusion and O out-diffusion. The contact surface becomes
rough and textured. 相似文献
16.
Boyko V. M. Verevkin S. S. Kolin N. G. Korulin A. V. Merkurisov D. I. Polyakov A. Y. Chevychelov V. A. 《Semiconductors》2011,45(1):134-140
Effect of irradiation with high reactor-neutron fluences (Φ = 1.5 × 1017-8 × 1019 cm−2) and subsequent heat treatments in the temperature range 100–1000°C on the electrical properties and lattice constant of
epitaxial GaN layers grown on an Al2O3 substrate is considered. It is shown that, with the neutron fluence increasing to (1–2) × 1018 cm−2, the resistivity of the material grows to values of about 1010 Ω cm because of the formation of radiation defects, and, with the fluence raised further, the resistivity passes through
a maximum and then decreases to 2 × 106 Ω cm at 300 K, which is accounted for by the appearance of a hopping conductivity via deep defects in the overlapping outer
parts of disordered regions. With the neutron fluence raised to 8 × 1019 cm−2, the lattice constant c increases by 0.38% at a nearly unchanged parameter a. Heat treatment of irradiated samples at temperatures as high as 1000°C does not fully restore the lattice constant and the
electrical parameters of the material. 相似文献
17.
Thin films of InP were deposited on single crystals and thin films of CdS by the planar reactive deposition technique. Good
local epitaxy was observed on single crystals of CdS as well as InP and GaAs. The electrical evaluation of unintentionally
doped films on semi-insulating InP substrates show them to be n-type with room temperature electron concentrations ranging
from 5 × 1016 cm−3 to 5 × 1017 cm−3 and mobilities up to 1350 cm2/Vsec. For films intentionally doped with Mn and Be, p-type films were obtained. For Mn doping (deep acceptor level), room
temperature mobilities as high as 140 cm2/Vsec and free carrier concentrations as low as 5 × 1016 cm−3 (with dopant level of 3 × 1018 cm−3) were obtained. For Bedoped films, free carrier concentrations of about 5 × 1018 cm−3 and mobilities of 20 cm2/Vsec were found. Scanning electron microscope and microprobe pictures show appreciable interdiffusion between the InP/CdS
thin-film pair for InP deposited at 450°C. The loss of Cd from the CdS and the presence of an indium-cadmium-sulfur phase
at the InP/CdS interface were observed. Interdiffusion is alleviated for InP deposition at lower temperatures.
Supported in part by ERDA and AFOSR. 相似文献
18.
Electrical activation studies of Al
x
Ga1−x
N (x = 0.45 and 0.51) implanted with Si for n-type conductivity have been made as a function of ion dose and anneal temperature. Silicon ions were implanted at 200 keV
with doses ranging from 1 × 1014 cm−2 to 1 × 1015 cm−2 at room temperature. The samples were subsequently annealed from 1150°C to 1350°C for 20 min in a nitrogen environment. Nearly
100% electrical activation efficiency was successfully obtained for the Si-implanted Al0.45Ga0.55N samples after annealing at 1350°C for doses of 1 × 1014 cm−2 and 5 × 1014 cm−2 and at 1200°C for a dose of 1 × 1015 cm−2, and for the Al0.51Ga0.49N implanted with silicon doses of 1 × 1014 cm−2 and 5 × 1014 cm−2 after annealing at 1300°C. The highest room-temperature mobility obtained was 61 cm2/V s and 55 cm2/V s for the low-dose implanted Al0.45Ga0.55N and Al0.51Ga0.49N, respectively, after annealing at 1350°C for 20 min. These results show unprecedented activation efficiencies for Al
x
Ga1−x
N with high Al mole fractions and provide suitable annealing conditions for Al
x
Ga1−x
N-based device applications. 相似文献
19.
Titanium (15 nm)/aluminum (60 nm)/rhenium (20 nm)/gold (50 nm) ohmic contacts to moderately doped n-type GaN (4.07×1018 cm−3) have been investigated as a function of annealing temperature. It is shown that the current-voltage (I–V) characteristics
of the contacts are improved upon annealing at temperatures in the range of 550–750°C. Specific contact resistance as low
as 1.3 × 10−6 Ωcm2 is obtained after annealing at 750°C for 1 min in a nitrogen ambient. X-ray photoemission spectroscopy (XPS) results show
that the Ga 2p core level for the sample annealed at 750°C shifts toward the high binding side by 0.71 eV compared with that
of the as-deposited one. It is also shown that the contact does not seriously suffer from thermal degradation even when annealed
at 750°C for 30 min. Based on Auger electron spectroscopy (AES), glancing angle x-ray diffraction (GXRD), and XPS results,
possible explanations for the annealing-induced improvement of the ohmic behavior are described and discussed. 相似文献
20.
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