Gallium nitride (GaN) and its allied binaries InN and AIN as well as their ternary compounds have gained an unprecedented attention due to their wide-ranging applications encompassing green, blue, violet, and ultraviolet (UV) emitters and detectors (in photon ranges inaccessible by other semiconductors) and high-power amplifiers. However, even the best of the three binaries, GaN, contains many structural and point defects caused to a large extent by lattice and stacking mismatch with substrates. These defects notably affect the electrical and optical properties of the host material and can seriously degrade the performance and reliability of devices made based on these nitride semiconductors. Even though GaN broke the long-standing paradigm that high density of dislocations precludes acceptable device performance, point defects have taken the center stage as they exacerbate efforts to increase the efficiency of emitters, increase laser operation lifetime, and lead to anomalies in electronic devices. The p...

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Luminescence properties of defects in GaN

Wide bandgap semiconductors show superior material properties enabling potential power device operation at higher temperatures, voltages, and switching speeds than current Si technology. As a result, a new generation of power devices is being developed for power converter applications in which traditional Si power devices show limited operation. The use of these new power semiconductor devices will allow both an important improvement in the performance of existing power converters and the development of new power converters, accounting for an increase in the efficiency of the electric energy transformations and a more rational use of the electric energy. At present, SiC and GaN are the more promising semiconductor materials for these new power devices as a consequence of their outstanding properties, commercial availability of starting material, and maturity of their technological processes. This paper presents a review of recent progresses in the development of SiC- and GaN-based power semiconductor devices together with an overall view of the state of the art of this new device generation.

A Survey of Wide Bandgap Power Semiconductor Devices

An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Semiconductor device, and manufacturing method thereof

and Perspectives Sophie Carenco,†,‡,§,∥,⊥ David Portehault,*,†,‡,§ Ced́ric Boissier̀e,†,‡,§ Nicolas Meźailles, and Cleḿent Sanchez*,†,‡,§ †Chimie de la Matier̀e Condenseé de Paris, UPMC Univ Paris 06, UMR 7574, Colleg̀e de France, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France ‡Chimie de la Matier̀e Condenseé de Paris, CNRS, UMR 77574, Colleg̀e de France, 11 Place Marcellin Berthelot, 75231 Paris Cedex 05, France Chimie de la Matier̀e Condenseé de Paris, Colleg̀e de France, 11 Place Marcellin Berthelot, 75231 Paris Cedex 05, France Laboratory Heteroelements and Coordination, Chemistry Department, Ecole Polytechnique, CNRS-UMR 7653, Palaiseau, France

Nanoscaled metal borides and phosphides: recent developments and perspectives

Silicon carbide (SiC) power devices have been investigated extensively in the past two decades, and there are many devices commercially available now. Owing to the intrinsic material advantages of SiC over silicon (Si), SiC power devices can operate at higher voltage, higher switching frequency, and higher temperature. This paper reviews the technology progress of SiC power devices and their emerging applications. The design challenges and future trends are summarized at the end of the paper.

https://ieeexplore.ieee.org/ielaam/41/8031005/7815312-aam.pdf

Review of Silicon Carbide Power Devices and Their Applications

The first-order Raman frequency shifts of the A g (2) + B g (2) mode in a CaWO 4 crystal were measured in the temperature range of 77∼771 K. The frequency shift for this mode changes very slowly with increasing temperature. The temperature dependence of the frequency shift of the A g (2) + B g (2) mode was analyzed using the lattice dynamical perturbative treatment. We found that the quartic anharmonic term of the first-order perturbation, as well as the cubic term of the second-order one, and thermal expansion contribute to the temperature dependence of the frequency shift of the A g (2) + B g (2) mode in a CaWO 4 crystal.

Temperature Dependence of the Ag+Bg-Mode of Raman Shift for CaWO 4 Crystal

Isochronal annealing was performed on Mg-ion-implanted GaN under 1 GPa N2 ambient pressure for 5 min at temperatures of 1573–1753 K. Secondary ion mass spectrometry showed diffusion of Mg atoms and introduction of H atoms during annealing. Deeper diffusion was observed with increasing temperature. From Hall-effect measurements, p-type conductivity was found even for the sample with the lowest annealing temperature of 1573 K. For this sample, the acceptor activation ratio was 23% and the compensation ratio was 93%. The acceptor activation ratio increased to almost 100% and the compensation ratio decreased to 12% with increasing annealing temperature.

Isochronal annealing study of Mg-implanted p-type GaN activated by ultra-high-pressure annealing

Deposited SiN/SiO2 stack gate structures have been investigated to improve the 4H-SiC MOS interface quality. Capacitance-voltage measurements on fabricated SiN/SiO2 stack gate MIS capacitors have indicated that the interface state density is reduced by post-deposition annealing in N2O at 1300°C. The usage of thin SiN and increase in N2O-annealing time lead to a low interface state density of 1×1011 cm-2eV-1 at EC – 0.2 eV. Oxidation of the SiN during N2O annealing has resulted in improvement of SiC MIS interface. The fabricated SiN/SiO2 stack gate MISFETs demonstrate a high channel mobility of 32 cm2/Vs on (0001)Si face and 40 cm2/Vs on (000-1)C face.

Enhanced Channel Mobility in 4H-SiC MISFETs by Utilizing Deposited SiN/SiO2 Stack Gate Structures

We investigated majority and minority carrier traps in lightly doped n- and p-type 4H-SiC epitaxial layers before and after thermal oxidation using deep level transient spectroscopy and minority carrier transient spectroscopy. We detected oxidation-induced new minority carrier traps, HO1 (EV + 0.36 eV) and HO2 (EV + 0.54 eV) for n-type 4H-SiC, and EO1 (EC − 0.59 eV) and EO2 (EC − 0.84 eV) for p-type 4H-SiC after thermal oxidation at 1300 °C. After subsequent Ar annealing at 1550 °C, the HO1, HO2, and EO1 centers disappeared, whereas the concentration of the EO2 center increased. The properties of these carrier traps are discussed.

https://iopscience.iop.org/article/10.7567/APEX.8.111301/pdf

Oxidation-induced majority and minority carrier traps in n- and p-type 4H-SiC

Power devices are operated under harsh conditions, such as high currents and voltages, and so degradation of these devices is an important issue. Our group previously found significant increases in reverse leakage current after applying continuous forward current stress to GaN p-n junctions. In the present study, we identified the type of threading dislocations that provide pathways for this reverse leakage current. GaN p-n diodes were grown by metalorganic vapor phase epitaxy on freestanding GaN(0001) substrates with threading dislocation densities of approximately 3 × 105 cm-2. These diodes exhibited a breakdown voltage on the order of 200 V and avalanche capability. The leakage current in some diodes in response to a reverse bias was found to rapidly increase with continuous forward current injection, and leakage sites were identified by optical emission microscopy. Closed-core threading screw dislocations (TSDs) were found at five emission spots based on cross-sectional transmission electron microscopy analyses using two-beam diffraction conditions. The Burgers vectors of these dislocations were identified as [0001] using large-angle convergent-beam electron diffraction. Thus, TSDs for which b = 1c are believed to provide current leakage paths in response to forward current stress. 

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Jun Suda

Papers

Temperature Dependence of the Ag+Bg-Mode of Raman Shift for CaWO 4 Crystal

Isochronal annealing study of Mg-implanted p-type GaN activated by ultra-high-pressure annealing

Enhanced Channel Mobility in 4H-SiC MISFETs by Utilizing Deposited SiN/SiO2 Stack Gate Structures

Oxidation-induced majority and minority carrier traps in n- and p-type 4H-SiC

Identification of type of threading dislocation causing reverse leakage in GaN p–n junctions after continuous forward current stress