Toshiyuki Ohno

Influence of stacking faults on the performance of 4H–SiC Schottky barrier diodes fabricated on (112̄0) face

The influence of stacking faults (SFs) on the performance of 4H–SiC (1120) Schottky barrier diodes fabricated on the epilayer grown on the substrate which was grown in [1120] direction by the sublimation method was investigated. The number of SFs under the Schottky electrode was determined by KOH etching of (1100) face cross section. SFs were found to have a severe influence on the leakage current of reverse characteristic and Schottky barrier height. The leakage current is increased even though a few SFs exist under the electrode. The Schottky barrier height is also affected by the SF under the electrode.

Uniformity of 4H–SiC epitaxial layers grown on 3-in diameter substrates

Abstract Uniformity of thickness and carrier concentration of homo-epitaxial films grown on 3-in diameter 4H–SiC substrates using a horizontal hot-wall reactor has been investigated. From the comparison between the experimental results and temperature and gas flow simulation, it is found that the thickness (growth rate) distribution is closely related to the gas velocity distribution, and the carrier concentration distribution has strong correlation with the temperature distribution not on the surface of the susceptor plate but in the gas phase. It is pointed out that the growth rate uniformity of 3-in diameter wafer is degraded by the gas flow disturbance near the susceptor’s side walls, and the carrier concentration uniformity is strongly related to the gas phase reaction of nitrogen containing species, such as N 2 and/or others.

Fabrication of 1.4-kV mesa-type p+-n diodes with avalanche breakdown and without forward degradation on high-quality 6H-SiC substrate

Using our own substrate growth and epitaxial growth techniques, we fabricated a 1.4-kV mesa-type 6H-SiC p+–n diode with an ideal avalanche breakdown and without forward degradation. The 6H-SiC substrates were grown on Lely crystals with no micropipes and only minimal defects. A p+–n junction was fabricated by chemical vapor deposition with p+/n− epitaxial films. We obtained 1.4-kV breakdown voltage, consistent with the ideal breakdown voltage calculated from the thickness and doping concentration of the drift layer. The application of 200-A/cm2 current stress in the forward direction produced no degradation, which is often observed with p–n diodes on normal substrates.

Characterization of the Forward Conduction of 4H-SiC Planar Junction Diode

The forward current conductions of the planar junct io diodes fabricated on 4H-SiC were analyzed in relation to defects. The forward curren t co duction above 2V followed the well-known exponential dependence for forward voltage. However , below 2V, some types of “excess current” were revealed. We classified these “excess currents ” a d found that some were related to micropipe defects, and the others were related to space-charg e limited currents. Introduction Silicon Carbide (SiC) has many intrinsic defects su ch as micropipes and dislocations, for example. The fabrication of the planar electronic devices re qui s selective doping, and when using SiC, fabrication can be only achieved by ion implantatio n because of the small diffusion coefficients of dopants in this material. Deep pn junctions of seve ral microns with high blocking voltage and low leakage currents require ion implantation by means of mega electron volt energy. After implantation, t he implanted dopants predominantly occupy interstitial lattice sites, where they are usually electrically inactive. Therefore, a thermal annealing process is necessary to electrically activate the implanted dopants and to reduce lattice damage. Transmission electron microscopy (TEM) observations show that secondary defects are formed during annealing and t h t they remain after annealing. These defects are dislocation loops having diameters of several nanom eters. (1)-(3) How defects affect device characteristics and what kind of effects they have are not known. Generally, it is said that these defects affect the rev rse characteristics of the diodes, -Relating defects to the reverse characteristics is very difficult. -b ecause changes in the reverse characteristics are v ery small, and we only get the information that a breakdown is a avalanche or not, or the leakage current is smal l or not. However, we found that the forward characte istics below 2V are different from those above 2V, and we think these reflect the defects. In this wor k, we classify the forward characteristics of plana r junction diodes in relation to defects. Materials Science Forum Online: 2003-09-15 ISSN: 1662-9752, Vols. 433-436, pp 835-838 doi:10.4028/www.scientific.net/MSF.433-436.835