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Acceptor levels of the carbon vacancy in 4 <i>H</i> -SiC: Combining Laplace deep level transient spectroscopy with density functional modeling
摘要： We provide direct evidence that the broad Z1/2 peak, commonly observed by conventional deep level transient spectroscopy in as-grown and at high concentrations in radiation damaged 4H-SiC, has two components, namely, Z1 and Z2, with activation energies for electron emissions of 0.59 and 0.67 eV, respectively. We assign these components to Z?1/2 + e? → Z?1/2 → Z?1/2 + 2e? transition sequences from negative-U ordered acceptor levels of carbon vacancy (V_C) defects at hexagonal/pseudo-cubic sites, respectively. By employing short filling pulses at lower temperatures, we were able to characterize the first acceptor level of V_C on both sub-lattice sites. Activation energies for electron emission of 0.48 and 0.41 eV were determined for Z1(?/0) and Z2(?/0) transitions, respectively. Based on trap filling kinetics and capture barrier calculations, we investigated the two-step transitions from neutral to doubly negatively charged Z1 and Z2. Positions of the first and second acceptor levels of V_C at both lattice sites, as well as (?/0) occupancy levels, were derived from the analysis of the emission and capture data.
关键词： density functional theory,acceptor levels,deep level transient spectroscopy,negative-U ordering,carbon vacancy,4H-SiC
更新于2025-09-23 15:23:52
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Investigation of Trap-Induced Threshold Voltage Instability in GaN-on-Si MISHEMTs
摘要： It is shown that an EC–0.90 eV trap in commercial AlGaN/GaN MISHEMTs grown on a Si (111) substrate is responsible for a ?1.8-V threshold voltage (VT) instability using a combination of defect spectroscopy and double-pulsed current–voltage measurements. The EC ? 0.90 eV trap is located in the GaN buffer and is emptied by high drain biases in pinch-off, which raises the trap above the Fermi level in the GaN buffer. This trap also exhibits both fast and slow recovery processes that are explained by the availability of free electrons throughout the depth of the GaN buffer and the trapping process that depletes the free electron concentration. TCAD modeling is used to demonstrate this process and also to show why there is not a significant increase in buffer leakage current after the large negative VT shift due to this trap. This demonstrates that optimizing buffer designs are critical for ideal device performance.
关键词： deep-level transient spectroscopy (DLTS),isothermal,GaN-on-Si,threshold voltage instability,metal-insulator-semiconductor high electron mobility transistors (MISHEMTs),Capture process,trap
更新于2025-09-23 15:22:29
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Electrical characterization of HVPE GaN containing different concentrations of carbon dopants
摘要： A comprehensive study of the electrical characteristics in Schottky diodes made of GaN:C grown by HVPE technology has been reported. The Schottky junctions were made of Ni/Au (25/200 nm) metal stack and ohmic contacts were fabricated by the Ti/Al/Ni/Au (30/90/20/100 nm) e-beam deposition of the metal thin-films followed by the rapid thermal annealing. A good quality of the fabricated Schottky diodes has been proved by considering the transient shape using a pulsed technique of the barrier evaluation under linearly increasing voltage (BELIV). The concentrations of equilibrium carriers of 1×1011 cm-3 and of 2×1010 cm-3 have been evaluated for relatively low and high carbon density doped samples, respectively, using photo-capacitance characteristics dependent on excitation intensity. The effective mobility of carriers of μeff=610 cm2/Vs has been estimated by considering the serial resistance variations dependent on excitation density, through analysis of delay times appeared in formation of peaks within BELIV transients. The optical deep level transient spectroscopy has shown that thermal emission from the rather shallow centres prevails. The centres, ascribed to vacancies as well as to carbon on Ga site, have been identified. It has been demonstrated that Schottky junctions made of heavy carbon doped (NC≥1018 cm-3) HVPE GaN material are capable to withstand voltages of ≥300 V.
关键词： barrier evaluation by linearly increasing voltage pulsed technique,transient current technique,Schottky diodes,carbon doped HVPE GaN grown on Ammono substrates,deep level transient spectroscopy
更新于2025-09-23 15:21:21
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A DLTS Perspective on Electrically Active Defects in Plated Crystalline Silicon n <sup>+</sup> p Solar Cells
摘要： Laser ablation (LA) has been compared with standard wet etching for contact opening in crystalline silicon n+p solar cells, from a perspective of electrically active defects, assessed by Deep-Level Transient Spectroscopy (DLTS). Copper metallization is employed, including a plated nickel diffusion barrier. It is shown that a hole trap around 0.17 eV above the valence band is systematically present in the depletion region of the junctions, irrespective of the contact opening method. This level could correspond with the substitutional nickel donor level in silicon and indicates that Ni in-diffusion occurs during the contact processing. No clear evidence for the presence of electrically active copper has been found. In addition, two other hole traps H2 and H3, belonging to point defects, have been observed after wet etching and standard LA, while for the highest laser power (hard LA) a broad band develops around 175 K, which is believed to be associated with dislocations, penetrating the p-type base region. Evidence will also be given for the impurity decoration of the dislocations, which enhances their electrical activity.
关键词： Deep-Level Transient Spectroscopy (DLTS),copper metallization,electrically active defects,laser ablation,nickel diffusion barrier,wet etching,crystalline silicon n+p solar cells
更新于2025-09-11 14:15:04
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Charge transient behaviour and spectroscopic ellipsometry characteristics of TiN/HfSiO MOS capacitors
摘要： A combination of two powerful techniques, namely, charge Deep level transient spectroscopy and spectroscopic ellipsometry is employed on atomic layer deposited Si-metal oxide semiconductor capacitors (MOSCAPs) to investigate the energy ef?ciency of the physical process. Ultra-thin TiN/HfSiO acted as gate-dielectric stack on Si substrate was carefully subjected to rapid thermal processing and subsequent spectroscopic measurements to determine the transient behaviour of charges and electro-optical characteristics. Some key parameters such as trap concentration, activation energy required to surmount the traps, capture cross section, refractive index and extinction coef?cient are found to play an important role in order to assess the energy ef?ciency of the devices both in terms of post-process quality of the retained surface and residual ef?ciency of the process by virtue of dynamics at atomistic scales. The results may provide a useful insight to the Si manufacturing protocols at ever decreasing nodes with desirable energy ef?ciency.
关键词： energy efficiency,charge Deep level transient spectroscopy,MOSCAPs,spectroscopic ellipsometry,TiN/HfSiO
更新于2025-09-10 09:29:36
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Border trap evaluation for SiO <sub/>2</sub> /GeO <sub/>2</sub> /Ge gate stacks using deep-level transient spectroscopy
摘要： A border trap (BT) evaluation method was established for SiO2/GeO2/Ge gate stacks by using deep-level transient spectroscopy with a lock-in integrator. Ge metal-oxide-semiconductor capacitors (MOSCAPs) with SiO2/GeO2/Ge gate stacks were fabricated by using different methods. The interface trap (IT) and BT signals were successfully separated based on their different dependences on the intensity of injection pulses. By using p-type MOSCAPs, BTs at the position of 0.4 nm from the GeO2/Ge interface were measured. The energy of these BTs was centralized at the position near to the valence band edge of Ge, and their density (Nbt) was in the range of 1017–1018 cm?3. By using n-type MOSCAPs, BTs at the position range of 2.8–3.4 nm from the GeO2/Ge interface were measured, of which Nbt varied little in the depth direction. The energy of these BTs was distributed in a relatively wide range near to the conduction band edge of Ge, and their Nbt was approximately one order of magnitude higher than those measured by p-MOSCAPs. This high Nbt value might originate from the states of the valence alternation pair with energy close to 1 eV above the conduction band edge of Ge. We also found that Al post metallization annealing can passivate both ITs and BTs near to the valence band edge of Ge but not those near to the conduction band edge.
关键词： deep-level transient spectroscopy,valence band edge,conduction band edge,interface trap,border trap,Ge metal-oxide-semiconductor capacitors
更新于2025-09-09 09:28:46