Nao Miyamoto

Performance limiting surface defects in SiC epitaxial p-n junction diodes

Effects of surface defects on performance of kV-class 4H- and 6H-SiC epitaxial p-n junction diodes were investigated. The perimeter recombination and generation, instead of the bulk process, are responsible for forward recombination current and reverse leakage current of the diodes, respectively. Mapping studies of surface morphological defects have revealed that triangular-shaped defects severely degrade high-blocking capability of the diodes whereas shallow round pits and scratch give no direct impact. Device-killing defects in SiC epilayers are discussed based on breakdown voltage mapping. Effective minority carrier lifetimes are mainly limited not by bulk recombination but by perimeter recombination.

Remarkable lattice recovery and low sheet resistance of phosphorus-implanted 4H–SiC (112̄0)

High-dose ion implantation of phosphorus into 4H–SiC has been investigated. Phosphorus ion implantation with a 1×1016 cm−2 dose at 800 °C into 4H–SiC (0001) has resulted in a sheet resistance of 80 Ω/□ after annealing at 1700 °C. A similar sheet resistance of 110 Ω/□ was achieved even by room-temperature implantation when 4H–SiC (1120) was employed, owing to excellent recrystallization of this face revealed by Rutherford backscattering channeling spectroscopy. The sheet resistance could be further reduced down to 27 Ω/□ by 800 °C implantation into 4H–SiC (1120) followed by annealing at 1700 °C. 4H–SiC (1120) showed a very flat surface after annealing.

High-energy (MeV) Al and B ion implantations into 4H-SiC and fabrication of pin diodes

High-energy (MeV) implantation of Al+ or B+ into 4H-SiC epilayers has been investigated. A 3 μm deep pn junction was formed by multiple-step Al+ or B+ implantation with implantation energies up to 6.2 or 3.4 MeV, respectively. Rutherford backscattering channeling and cross-sectional transmission electron microscopy analyses have revealed residual damages in the implanted layers even after high-temperature annealing at 1600–1800 °C. Nevertheless, high electrical activation ratios over 90% have been achieved for both Al+- and B+-implanted layers by annealing at 1800 °C. Mesa pin diodes with a 15-μm-thick i layer formed by MeV implantation have exhibited high breakdown voltages of 2860–3080 V. The reverse characteristics of diodes have been substantially improved by increasing annealing temperature up to 1800 °C. The diode performance is discussed with the results of deep level analyses near the junctions.

Effects of surface defects on the performance of 4H– and 6H–SiC pn junction diodes

Abstract Effects of surface defects on performance of kV-class 4H– and 6H–SiC epitaxial mesa pn junction diodes were investigated. Mapping studies of surface morphological defects have revealed that triangular-shaped defects severely degrade high-blocking capability of the diodes whereas shallow round pits and scratch give no direct impact. The perimeter recombination and generation, instead of the bulk process, are responsible for forward recombination current and reverse leakage current of the diodes, respectively. Effective minority carrier lifetimes are mainly limited not by bulk recombination but by perimeter recombination.

Avalanche phenomena in 4H-SiC p-n diodes fabricated by aluminum or boron implantation

Characteristics of p-n junction fabricated by aluminum-ion (Al/sup +/) or boron-ion (B/sup +/) implantation and high-dose Al/sup +/-implantation into 4H-SiC (0001) have been investigated. By the combination of high-dose (4/spl times/10/sup 15/ cm/sup -2/) Al/sup +/ implantation at 500/spl deg/C and subsequent annealing at 1700/spl deg/C, a minimum sheet resistance of 3.6 k/spl Omega///spl square/ (p-type) has been obtained. Three types of diodes with planar structure were fabricated by employing Al+ or B+ implantation. B/sup +/-implanted diodes have shown higher breakdown voltages than Al/sup +/-implanted diodes. A SiC p-n diode fabricated by deep B+ implantation has exhibited a high breakdown voltage of 2900 V with a low on-resistance of 8.0 m/spl Omega/cm/sup 2/ at room temperature. The diodes fabricated in this study showed positive temperature coefficients of breakdown voltage, meaning avalanche breakdown. The avalanche breakdown is discussed with observation of luminescence.

Variation of Size and Density of Pyramidal Hillock during Epitaxial Growth of Silicon Using Dichlorosilane Gas

For Si epitaxial growth on Si(111) with dichlorosilane (SiH 2 Cl 2 ), the kinetics of nucleation and growth of pyramidal hillock (PH) has been investigated by measuring the variations of size and density of PH as a function of growth temperature, SiH 2 Cl 2 volume concentration, and gas pressure. The nucleation of PH can be considerably suppressed by reducing SiH 2 Cl 2 volume concentration or gas pressure under a constant SiH 2 Cl 2 mole concentration. The reason for the reduction in PH density is discussed in terms of the previous findings that the nucleation of PH is always associated with the existence of growth defects such as stacking faults, dislocations, or polycrystalline Si. Furthermore, the PH size increases in proportion to the layer thickness and decreases drastically as the PH density increases or the growth temperature is raised. This indicates that the growth of PH is dominated by three factors : layer thickness, distribution of Si adatoms into the individual PH, and surface migration of Si adatoms. Thus it is likely that PH plays a role of growth site as kink and step edge, whereas Si adatoms are more preferentially incorporated into step and kink sites during Si growth.