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Diamond is a promising material for future high-voltage applications because of its high critical electric field. This property leads to new constraints on the used termination structure, especially in terms of an electric field value. For this reason, new termination architectures based on a field plate are proposed for diamond Schottky diodes. Using the finite-element simulations with the Sentaurus technology computer-aided design software, a new field plate structure has been proposed. Simple variations in the classic field plate architecture were sufficient to increase the breakdown voltage from 1632 to 2141 V at 700 K, but not to reduce the electric field value at the edges of the field plate. Several termination topologies have been proposed to solve this problem. Parametric simulations were used to optimize the geometrical termination structure in order to reduce the electric field peak value at its edge while maintaining a high breakdown voltage. The new solutions have helped to reduce the maximum electric field from 57 down to 22.7 MV/cm. [ABSTRACT FROM AUTHOR]

Using finite element simulations with Sentaurus TCAD (Technology Computer-Aided Design) software, a progress from simple and classic termination for a Schottky diode to new topology termination has been studied in this paper. A polyimide trench under field plate termination has been used. The efficiency increases from 67% for a simple field plate with optimum parameters up to 97%. The maximum electric field in the termination dielectric has been evaluated also. A wide study of the termination geometry has been made in order to extract the optimum parameters in two directions. The first one is to obtain a high efficiency regarding the breakdown voltage, and the second one is to have the minimum electric field peak at the termination edge. [ABSTRACT FROM AUTHOR]

In high current, high voltage, high temperature (T>125^\circC) power applications, commercially available conventional silicon thyristors are not suited because they present high leakage current. In this context, this paper presents a high-symmetrical (voltage) thyristor structure that presents a lower leakage current and higher breakover voltage as compared with the conventional thyristor at T>125^\circC. It is shown through 2-D physical simulations that the replacement of the P-emitter of a standard symmetrical thyristor by a judicious association of P diffusions and Schottky contacts at the anode side contributes to the reduction of the leakage current in the forward blocking state at high temperature. A fine tune of the anode side configuration will improve the forward OFF-state behavior with only a negligible ON-state voltage drop degradation. Moreover, the comparison with the conventional anode short thyristor shows that the insertion of Schottky contacts leads to the same improvements in terms of OFF-state forward breakover voltage and leakage current and also presents a high reverse blocking voltage. [ABSTRACT FROM PUBLISHER]

N-doped homo-epitaxial GaN samples grown on freestanding GaN substrates have been investigated by micro-Raman spectroscopy. Quantitative analysis of the E 2 h and the A1(LO) modes' behavior has been performed while intentionally increasing the carrier density using silicon doping. We noticed that as the carrier concentration increases up to 1.8 × 1018 cm−3, the E 2 h mode remains unchanged. On the other hand, when the doping gets higher, the A1(LO) position shifts to a higher frequency range, its width becomes larger, and its intensity drastically diminishes. This change in the A1(LO) behavior is due to its interaction and its coupling with the free negative charge carriers. Furthermore, we calibrated the A1(LO) frequency position shift as a function of the n-carrier concentration. We found out that for low n doping, the change in the A1(LO) position can be considered as a linear variation while in the overall doping range, a sigmoid growth trend with a Boltzmann fit can be tentatively applied to describe the A1(LO) position shift. This calibration curve can also be used to describe the coupling strength between the carriers and the A1(LO) phonon. Eventually, this study shows that micro-Raman spectroscopy is a powerful non-destructive tool to probe the doping concentration and the crystalline quality of GaN material with a microscopic spatial resolution. [ABSTRACT FROM AUTHOR]

This paper reports comprehensive characterization of vertical GaN-on-GaN Schottky barrier diodes (SBDs) fabricated on free-standing GaN substrates. The GaN active layer properties are evaluated by atomic force microscopy (AFM), secondary-ion mass spectrometry (SIMS), micro-Raman spectroscopy, cathodoluminescence (CL), and deep-level transient Fourier spectroscopy (DLTFS). The GaN SBDs exhibit near-unity ideality factor (n = 1.1), promising Schottky barrier height (SBH) of Φ B = 0.82 eV, low turn-on voltage ∼0.56 V, leakage current density of J R < 5.5 × 10−6 Acm−2 at −100 V, breakdown voltage V BR < −200 V, and less interface state density (N SS < 5 × 1012 eV−1 cm−2) at the Ni/GaN Schottky contact. The forward and reverse current transport mechanisms of the SBD are identified by fitting analysis of measured J-V. Weak temperature dependence of Φ B and n is detected from I–V-T measurements. Similar traps at E C - 0.18 eV and E C - 0.56 are identified in the various SBDs from DLTFS, signifying that these traps are omnipresent defects in the epilayer. • Comprehensive characterizations are carried out for vertical GaN-on-GaN Schottky barrier diodes (SBDs). • Typical electrical characteristics of quasi-ideal vertical GaN-on-GaN SBDs are reported. • Various current transport mechanisms involved during forward and reverse characteristics of the SBD are identified. • The GaN active layer properties are evaluated by AFM, SIMS, micro-Raman spectroscopy, cathodoluminescence (CL). • Furthermore, traps in the GaN diodes are detected by deep level transient Fourier spectroscopy (DLTFS). [ABSTRACT FROM AUTHOR]