The behavior of the I-V-T characteristics of inhomogeneous (Ni∕Au)–Al[sub 0.3]Ga[sub 0.7]N∕AlN∕GaN heterostructures at high temperatures (original) (raw)
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Journal of Applied Physics, 2007
We investigated the behavior of the forward bias current-voltage-temperature ͑I-V-T͒ characteristics of inhomogeneous ͑Ni/ Au͒-Al 0.3 Ga 0.7 N / AlN / GaN heterostructures in the temperature range of 295-415 K. The experimental results show that all forward bias semilogarithmic I-V curves for the different temperatures have a nearly common cross point at a certain bias voltage, even with finite series resistance. At this cross point, the sample current is temperature independent. We also found that the values of series resistance ͑R s ͒ that were obtained from Cheung's method are strongly dependent on temperature and the values abnormally increased with increasing temperature. Moreover, the ideality factor ͑n͒, zero-bias barrier height ͑⌽ B0 ͒ obtained from I-V curves, and R s were found to be strongly temperature dependent and while ⌽ B0 increases, n decreases with increasing temperature. Such behavior of ⌽ B0 and n is attributed to Schottky barrier inhomogeneities by assuming a Gaussian distribution ͑GD͒ of the barrier heights ͑BHs͒ at the metal/semiconductor interface. We attempted to draw a ⌽ B0 versus q /2kT plot in order to obtain evidence of the GD of BHs, and the values of ⌽ B0 = 1.63 eV and 0 = 0.217 V for the mean barrier height and standard deviation at a zero bias, respectively, were obtained from this plot. Therefore, a modified ln͑I 0 / T 2 ͒ − q 2 0 2 /2͑kT͒ 2 versus q / kT plot gives ⌽ B0 and Richardson constant A * as 1.64 eV and 34.25 A / cm 2 K 2 , respectively, without using the temperature coefficient of the barrier height. The Richardson constant value of 34.25 A / cm 2 K 2 is very close to the theoretical value of 33.74 A / cm 2 K 2 for undoped Al 0,3 Ga 0,7 N. Therefore, it has been concluded that the temperature dependence of the forward I-V characteristics of the ͑Ni/ Au͒-Al 0.3 Ga 0.7 / AlN / GaN heterostructures can be successfully explained based on the thermionic emission mechanism with the GD of BHs.
Microelectronic Engineering, 2008
The temperature dependence of capacitance-voltage (C-V) and the conductance-voltage (G/w-V) characteristics of (Ni/Au)/Al 0.3 Ga 0.7 N/AlN/GaN heterostructures were investigated by considering the effect of series resistance (R s ) and interface states N ss in a wide temperature range (79-395 K). Our experimental results show that both R s and N ss were found to be strongly functional with temperature and bias voltage. Therefore, they affect the (C-V) and (G/w-V) characteristics. The values of capacitance give two peaks at high temperatures, and a crossing at a certain bias voltage point ($3.5 V). The first capacitance peaks are located in the forward bias region ($0.1 V) at a low temperature. However, from 295 K the second capacitance peaks appear and then shift towards the reverse bias region that is located at $À4.5 V with increasing temperature. Such behavior, as demonstrated by these anomalous peaks, can be attributed to the thermal restructuring and reordering of the interface states. The capacitance (C m ) and conductance (G/w-V) values that were measured under both reverse and forward bias were corrected for the effect of series resistance in order to obtain the real diode capacitance and conductance. The density of N ss , depending on the temperature, was determined from the (C-V) and (G/w-V) data using the Hill-Coleman Method.
Surface and Interface Analysis, 2010
The profile of the interface state densities (Nss) and series resistances (Rs) effect on capacitance–voltage (C–V) and conductance-voltage (G/ω–V) of (Ni/Au)/AlxGa1−xN/AlN/GaN heterostructures as a function of the temperature have been investigated at 1 MHz. The admittance method allows us to obtain the parameters characterizing the metal/semiconductor interface phenomena as well as the bulk phenomena. The method revealed that the density of interface states decreases with increasing temperature. Such a behavior of Nss can be attributed to reordering and restructure of surface charges. The value of series Rs decreases with decreasing temperature. This behavior of Rs is in obvious disagreement with that reported in the literature. It is found that the Nss and Rs of the structure are important parameters that strongly influence the electrical parameters of (Ni/Au)/AlxGa1−xN/AlN/GaN(x = 0.22) heterostructures. In addition, in the forward bias region a negative contribution to the capacitance C has been observed, that decreases with the increasing temperature. Copyright © 2010 John Wiley & Sons, Ltd.
Surface and Interface …, 2010
x = 0.22) heterostructures with and without a passivation layer of the SiN x were fabricated in order to see the effect of the insulator layer on the main electrical parameters such as zero-bias barrier height (BH) ( B0 ), ideality factor (n), series resistance (R s ) of the structure, and the interface state density (N ss ). Some of these parameters were determined from both I-V and admittance (C-V and G/ω -V) measurements at room temperature and at 1 MHz and were compared. The experimental results show that the value of N ss in a Schottky contact without passivation is nearly 1 order of magnitude larger than that in a Schottky contact with SiN x passivation layers. Also, the values of R s increase with the increasing thickness of the passivation layer. In the forward bias region, the negative values of capacitance are an attractive result of this study. This negative capacitance disappears in presence of the passivation layer.
Electron heating in Al0.15Ga0.85N/GaN heterostructures grown on p-type Si
Physica E: Low-dimensional Systems and Nanostructures, 2007
The transport behaviors of two GaN/AlGaN two-dimensional electron systems (2DESs) grown on Si substrates were studied, and a SiN x treatment employed in sample fabrication enhanced the conductance of one of the 2DESs. We study the electron heating effect in the 2DESs experimentally, with resistances as self-thermometers. The relation of T e I1.42wasobtained,whichisincontrasttoTeI 1.42 was obtained, which is in contrast to T e I1.42wasobtained,whichisincontrasttoTeI 0.5 in the resistivity peaks in a GaAs/AlGaAs 2DES. This may be caused by the scattering effect in this sample. r
physica status solidi (a), 2012
The electron transport properties in Al 0.25 Ga 0.75 N/AlN/GaN/ In x Ga 1Àx N/GaN double heterostructures with various indium compositions and GaN channel thicknesses were investigated. Samples were grown on c-plane sapphire substrates by MOCVD and evaluated using variable temperature Hall effect measurements. In order to understand the observed transport properties, various scattering mechanisms, such as acoustic phonon, optical phonon, interface roughness, background impurity, and alloy disorder, were included in the theoretical model that was applied to the temperature-dependent mobility data. It was found that low temperature (T < 160 K) mobility is limited only by the interface roughness scattering mechanism, while at high temperatures (T > 160 K), optical phonon scattering is the dominant scattering mechanism for AlGaN/ AlN/GaN/InGaN/GaN heterostructures. The higher mobility of the structures with InGaN back barriers was attributed to the large conduction band discontinuity obtained at the channel/ buffer interface, which leads to better electron confinement.
Temperature dependence of the specific resistance in Ti∕Al∕Ni∕Au contacts on n-type GaN
Journal of Applied Physics, 2006
The temperature dependence of the specific resistance c in annealed Ti/ Al/ Ni/ Au contacts on n-type GaN was monitored, obtaining information on the current transport mechanisms. After annealing at 600°C, the contacts exhibited a rectifying behavior and became Ohmic only after high temperature processes ͑Ͼ700°C͒, with c in the low 10 −5 ⍀ cm 2 range. The results demonstrated that the current transport is ruled by two different mechanisms: thermoionic field emission occurs in the contacts annealed at 600°C, whereas field emission dominates after higher temperature annealing. The significant physical parameters related to the current transport, i.e., the Schottky barrier height and the carrier concentration under the contact, could be determined. In particular, a reduction of the Schottky barrier from 1.21 eV after annealing at 600°C to 0.81 eV at 800°C was determined, accompanied by a strong increase of the carrier concentration, i.e., from 2 ϫ 10 18 cm −3 in the as-prepared sample to 4.6ϫ 10 19 cm −3 in the annealed contacts. The electrical properties were correlated to the microstructure of the interfacial region, providing a scenario to explain the transition from Schottky to Ohmic behavior in annealed Ti/ Al/ Ni/ Au contacts.
Semiconductor …, 2008
Hall effect measurements on unintentionally doped Al 0.25 Ga 0.75 N/GaN/AlN heterostructures grown by metal organic chemical vapor deposition (MOCVD) were carried out as a function of temperature (20-300 K) and magnetic field (0-1.4 T). Magnetic-field-dependent Hall data are analyzed using the quantitative mobility spectrum analysis (QMSA) technique. The QMSA technique successfully separated electrons in the 2D electron gas (2DEG) at the Al 0.25 Ga 0.75 N/GaN interface from other 2D and 3D conduction mechanisms of the samples. 2DEG mobilities, carrier densities and conductivities of the investigated samples are compared at room temperature and low temperature (20 K). For a detailed investigation of the 2DEG-related growth parameters, the scattering analyses of the extracted 2DEG were carried out for all of the samples. Using the results of the scattering analyses, the relation between the growth and scattering parameters was investigated. Increments in the interface roughness (IFR) are reported with the increased GaN buffer growth temperatures. In addition, a linear relation between the deformation potential and interface roughness (IFR) scattering is pointed out for the investigated samples, which may lead to a better understanding of the mechanism of IFR scattering.
Bulletin of Materials …, 2007
Temperature dependent analysis to achieve better performance by reducing threshold current requirements and field intensity has been carried out for GaN/AlGaN heterostructure lasers. The mirror loss in the GaN cavity has been obtained as a function of temperature and cavity length. The quantum efficiency has been deduced for different values of cavity length. Dependence of recombination rate on band gap and temperature has been investigated. Threshold current density has been deduced for GaN lasers and effect of temperature on it has been investigated. The near field intensity analysis has been carried out at different temperatures for 10% aluminum mole fraction in GaN/AlGaN heterostructure lasers. Furthermore, the effective index and FWHM of near field has been investigated as a function of temperature. It has been deduced from our analysis that temperature has a dominant effect on the threshold conditions and near field intensity in the wide band gap GaN based lasers.
Electrical and Optical Characterization of Ni/Al0.3Ga0.7N/GaN Schottky Barrier Diodes
Journal of Electronic Materials, 2012
We report the electrical properties of n-InAsSb/n-GaSb heterojunctions as a function of the GaSb doping concentration. Because of the staggered type II band alignment, strong electron accumulation occurs on the InAsSb side. For low GaSb doping, depletion occurs on the GaSb side resulting in a Schottky-like junction as previously reported. As the GaSb doping increases, the built-in voltage as well as depletion width decreases as shown using self-consistent simulations. For GaSb doping levels above 5 ϫ 10 17 cm −3 , the junction loses its rectifying properties due to tunneling. Under zero and reverse bias voltage, the photoresponse of these diodes is solely due to the photovoltaic effect in the GaSb depletion region. For forward bias voltages Ͼ400 mV, we also observed a photoconductive response from the InAsSb layer. The proposed physical mechanism is quite different from the one suggested in a recent paper.