- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Molecular Dynamics Simulation on B3-GaN Thin Films under Nanoindentation
摘要： The B3-GaN thin film was investigated by performing large-scale molecular dynamics (MD) simulation of nanoindentation. Its plastic behavior and the corresponding mechanism were studied. Based on the analysis on indentation curve, dislocation density, and orientation dependence, it was found that the indentation depths of inceptive plasticity on (001), (110), and (111) planes were consistent with the Schmid law. The microstructure evolutions during the nanoindentation under different conditions were focused, and two formation mechanisms of prismatic loop were proposed. The “lasso”-like mechanism was similar to that in the previous research, where a shear loop can translate into a prismatic loop by cross-slip; and the extended “lasso”-like mechanism was not found to be reported. Our simulation showed that the two screw components of a shear loop will glide on another loop until they encounter each other and eventually produce a prismatic dislocation loop.
关键词： anisotropy,dislocation density,prismatic loops,B3-GaN,molecular dynamics
更新于2025-09-09 09:28:46
-
Creation of Two-Dimensional Electron Gas and Role of Surface Donors in III-N Metal-Oxide-Semiconductor High-Electron Mobility Transistors
摘要： The role of surface donors at the oxide/semiconductor interface of III-N metal-oxide-semiconductor (MOS) high-electron mobility transistors (HEMTs), by creating a two-dimensional electron gas (2DEG) and the device performance, are investigated. Al2O3/GaN/AlGaN/GaN MOS HEMTs show the surface donor density (Nd,surf ) of 2.2 (cid:1) 1013 cm(cid:3)2 which is increased up to 3.4 (cid:1) 1013 cm(cid:3)2 after post-deposition annealing. In the latter, surface donors fully compensate the surface polarization charge and the HEMT threshold voltage decreases substantially with the oxide thickness. On the other hand, an open-channel drain current is found to be independent of Nd,surf, while marginal trapping is completely removed when Nd,surf increases with annealing. Consequently, ionized surface donors behave like a fixed charge and are clearly distinguishable from trapping states. Open-channel 2DEG densities of (cid:4)1.1 (cid:1) 1013 cm(cid:3)2 are extracted from capacitance–voltage measurements. Similarly, recent data on enhancement-mode HfO2/InAlN/AlN/GaN MOS HEMTs are analyzed where Nd,surf is reduced down to (cid:3)2 while 2DEG densities reach (cid:4)2.7 (cid:1) 1013 cm(cid:3)2. It is suggested that under the open-channel condition, 2DEG is supplied also by an injecting source contact if Nd,surf is lower than the QW polarization charge. Our charge quantifications are supported by calculating energy-band diagrams.
关键词： oxide-semiconductor interfaces,AlGaN/GaN high-electron mobility transistors (HEMTs),polarization
更新于2025-09-09 09:28:46
-
Modeling charge density in AlGaN/AlN/InGaN/GaN-based double heterostructures including InGaN layer strain relaxation
摘要： An analytical model is presented to calculate the two-dimensional electron gas (2DEG) density and barrier height of bare surface AlGaN/AlN/InGaN/GaN double heterostructures, which use InGaN as the conducting layer. The basic model is derived from electrostatic analysis of the di?erent material interfaces. The e?ect of strain relaxation in the InGaN layer is also incorporated here. Further, the impact of a two-dimensional hole gas at the InGaN/GaN interface, formed when the InGaN layer thickness is high, has been considered. The presented results are seen to agree with the available experimental results. Thus, this model can be a useful tool in the design and modeling of InGaN-based III-nitride heterostructures.
关键词： two-dimensional hole gas,AlGaN/InGaN/GaN heterostructure,strain relaxation,two-dimensional electron gas
更新于2025-09-09 09:28:46
-
GaN metal-oxide-semiconductor devices with ZrO2 as dielectric layers
摘要： P-type GaN metal oxide semiconductors (MOS) with ZrO2 dielectrics have been fabricated. Here, H2O and O3 were selected as oxidizers for ZrO2 growth by atomic layer deposition. The MOS devices with O3 oxidant demonstrated a smaller ?at band voltage than that with H2O oxidant. A Ga2O3 interlayer was formed between GaN and O3-grown ZrO2, which can e?ectively decrease interfacial state density to 1.5 × 1011 cm?2. Meanwhile, the innovation of AlZnO (AZO)/Ag nanowires (AgNWs)/AlZnO composite electrodes can further decrease the ?at band voltage to about a half compared to that with traditional Cr/Au electrodes and superior electrical performance was achieved.
关键词： Silver nanowires,MOS,ZrO2,Atomic layer deposition,p-GaN
更新于2025-09-09 09:28:46
-
Analytical Gate Capacitance Models for Large-Signal Compact Model of AlGaN/GaN HEMTs
摘要： In this paper, analytical gate capacitance models for a large-signal compact model of AlGaN/GaN high-electron mobility transistors are proposed. Different from the MOSFET devices, different depletion regions on either side of the gate are fully considered for high-voltage GaN devices. The depletion regions are bias-dependent to implement the capacitance models into the large-signal compact model. A transfer function is proposed to characterize the switching behavior of the capacitances between on- and off-states, which is essential to describe all the states of a device, for example, operating at Class-B. Different from previous works, the current saturation phenomenon is taken into account in determining the intrinsic capacitances which are induced by nonstatic channel charge. The capacitance models can be easily implemented into the virtual-source-based model to accurately predict the S-parameters and large-signal output characteristics.
关键词： intrinsic capacitances,2-D electron gas (2DEG)-electrode fringing capacitances,AlGaN/GaN high-electron mobility transistors (HEMTs),large-signal compact model
更新于2025-09-09 09:28:46
-
The Effect of Proton Irradiation in Suppressing Current Collapse in AlGaN/GaN High-Electron-Mobility Transistors
摘要： Almost complete suppression of dynamic ON-resistance in AlGaN/GaN high-electron-mobility transistors is obtained by proton irradiation. In this paper, both small and large power transistors are characterized before and after 3-MeV proton irradiation at different fluences. The irradiated devices show a high robustness and for specific fluences unaltered threshold voltage and static ON-resistance. However, for fluences higher than 1013 cm?2, the dynamic ON-resistance is almost completely suppressed at 600 V and T = 150 °C. After irradiation, a measurable increase in OFF-state leakage current is observed, indicating an increase in the unintentionally doped (UID) GaN layer conductivity. We propose a technology computer-aided design supported model in which this conductivity increase leads to an increased deionization rate, ultimately reducing the dynamic ON-resistance.
关键词： high-electron-mobility transistor (HEMT),proton irradiation,Gallium nitride (GaN),dynamic ON-resistance
更新于2025-09-09 09:28:46
-
Hybrid Analog/Digital Linearization of GaN HEMT-Based Power Amplifiers
摘要： In this paper, we describe a hybrid analog/digital linearization scheme for GaN high-electron-mobility transistor (HEMT)-based power ampli?ers that consists of a novel analog feedforward circuit and a conventional generalized memory polynomial (GMP) digital predistorter (DPD). The analog circuit implements a nonlinear ?lter that compensates the long-term memory effects observed in GaN HEMTs due to the self-biasing behavior caused by electron-trapping phenomena. Experimental tests demonstrate that this linearization scheme achieves a level of intermodulation distortion 6.8 dB better than what can be achieved with just the use of the GMP DPD. This level of distortion is in compliance with the linearity speci?cations for multicarrier Global System for Mobile communications base station transmitters.
关键词： Analog linearization,long-term memory effects,GaN high-electron-mobility transistor (HEMT),power ampli?er (PA) linearization,digital predistortion (DPD),electron trapping
更新于2025-09-09 09:28:46
-
Enhanced structural and electrical properties of nonpolar a-plane p-type AlGaN/GaN superlattices
摘要： The nonpolar a-plane p-AlxGa1-xN/GaN superlattices (SLs) were successfully grown with metal organic chemical vapor deposition technology. The surface morphology, carrier concentration, layer thickness, and Al composition for the nonpolar a-plane p-AlxGa1-xN/GaN SLs were characterized by various kinds of technical tools. It was demonstrated that the thickness of the AlxGa1-xN and GaN layers in SLs was calculated to be 12 and 14.5 nm, respectively and the Al composition of the AlxGa1-xN layers in SLs was around 30%. Meanwhile, the results reveal that the surface morphology and carrier concentration of the nonpolar p-SLs could be improved remarkably with the Al composition-graded AlGaN buffer layer and the Mg-δ-doping process. Consequently, a root mean square value of 0.6 nm and a hole concentration of 4.2 × 1017 cm?3 were achieved.
关键词： Electrical properties,p-AlGaN/GaN superlattice,Nonpolar,Epitaxial growth
更新于2025-09-09 09:28:46
-
Optical admittance method for light-matter interaction in lossy planar resonators
摘要： Advanced optoelectronic simulation models are needed to study and optimize emerging photonic devices such as thin-film solar cells, lasers, and light-emitting diodes (LEDs). In particular, better tools are required for self-consistent modeling of coupled electrical and optical systems. The recently introduced quantized fluctuational electrodynamics (QFED) and the associated interference-exact radiative transfer equations have been developed for this purpose, but their use is in part complicated by the need to calculate the full dyadic Green’s functions. To make QFED and the underlying physical quantities more accessible for new device studies, we introduce a directly usable method where Green’s functions are obtained through optical admittances. The optical admittances can be solved analytically for piecewise-homogeneous layer structures and selected graded-index profiles, and numerically for arbitrary position-dependent refractive index profiles using well-known techniques. The solutions enable direct construction of the dyadic Green’s functions and all the related optical quantities. To give examples of the general applicability of the method, we calculate the local and nonlocal optical densities of states for selected devices, including GaN-based flip-chip LEDs and vertical-cavity surface-emitting lasers. Using only the rather simple framework presented in this paper, one can analyze energy transport in a wide range of planar photonic devices accurately without additional difficulties or inputs from external solvers.
关键词： dyadic Green’s functions,quantized fluctuational electrodynamics,GaN-based flip-chip LEDs,optoelectronic simulation models,photonic devices,optical admittances,vertical-cavity surface-emitting lasers
更新于2025-09-09 09:28:46
-
Effects of N2 and NH3 plasma exposure on the surface topography of p-GaN under quasi-atmospheric pressure
摘要： We used atomic force microscopy to characterize the surface topography of p-GaN exposed to N2 and NH3 plasma under quasi-atmospheric pressure using a microwave-excited plasma source with a microstrip line structure. The exposure time was varied from 2 to 20 min at a substrate temperature of 700 °C. Under both N2 and NH3 plasma exposure for 2 min, the ridge-shaped features on the surface of as-grown p-GaN dulled immediately and the surface roughness decreased remarkably, whereas the atomic step structure of the surface was maintained. The step crossing and bunching of the surface disappeared with increasing exposure time to both types of plasma. However, increasing the NH3 plasma exposure time to 20 min led to the formation of pits and appearance of particles along the step edges, resulting in drastic roughening of the surface. Thus, GaN surfaces can be smoothed without the destruction of their step structures via moderate plasma exposure under quasi-atmospheric pressure, and these plasma sources could prospectively be used in metal-organic chemical vapor deposition systems for nitride semiconductor growth.
关键词： microwave-assisted plasma,surface topography,N2 and NH3 plasma,atomic force microscopy,metal organic chemical vapor deposition,GaN
更新于2025-09-09 09:28:46