Papers by Keyword: p⁺n Diodes

Abstract: The dependence of the reverse current of 3C-SiC p+-n diodes on the temperature and on the reverse bias is measured and a model based on thermally-assisted tunneling is proposed to explain the dominating mechanism responsible for the leakage current. Taking into account an additional ohmic shunt resistance, the experimental reverse characteristics and thermal barrier heights B can sufficiently be reproduced.

Abstract: Electrical properties of p+n 4H-SiC(0001) diode formed by Al ion implantation to n-type epitaxial layer have been investigated as a function of Al doping concentration ranging from 1 x 1020 to 6 x 1020 /cm3 and the operation temperature. The n-type 4H-SiC(0001) epitaxial layer with a net donor concentration of 1 x 1016 /cm3 are multiply implanted by Al ions in the energy range from 30 to 170 keV at elevated temperature of 500 oC with a implantation layer thickness of 350 nm, followed by the annealing at 1900 oC for 1min using EBAS. On-state resistance of diode with Al concentration of 1 x 1020 /cm3 is estimated to be about 4.5 mcm2, while that for diode with Al concentration of 6 x 1020 /cm3 is 1.8 mcm2 at 25 oC. In the sample with Al concentration of 6 x 1020 /cm3 shows the positive temperature coefficient of on-state resistance of diode, while that for sample with Al concentration less than 3 x 1020 /cm3 is negative. The diode formed by Al implantation at the concentration of 6 x 1020 /cm3 is able to operate at the constant current density of 80 A/cm2 at the bias of 2.9 V independent to operation temperature.

Abstract: The current-voltage characteristics of Al+ implanted 4H-SiC p+n junctions show an important reduction of leakage currents with diode aging at room temperature. The case of a family of diodes that immediately after manufacture had forward current density increasing from 10-9 to 10-6 A/cm2 when biased from 0 and 2 V, and had a reverse leakage current density of @ 5×10-7 A/cm2 when biased at 100 V, is here presented and discussed. During diode manufacturing a post implantation annealing at 1600 °C for 30 min was followed by a 1000 °C 1 min treatment for metal contacts alloying. After 700 days of storage at room temperature, the diode reverse current density reached an asymptotical value of @ 4×10-11 A/cm2 that is four order of magnitude lower than the initial one. A 430 °C annealing that was made after 366 days is responsible of a decrease of one of these four orders of magnitude, but it does not interrupt the decreasing trend versus increasing time. This same annealing has been effective also for minimizing forward current for bias < 2 V, and sticking the diode turn-on voltage on 1.4 V and the current trend on an ideality factor of 2. These results show that in Al+ implanted 4H-SiC p+n junction there are defects that have an annihilation dynamic at very low temperatures, i.e. room temperature and 430 °C.

Abstract: An n-type 8° off-axis <0001> 4H-SiC epitaxial wafer was processed. The n-type epilayer had doping and thickness of, respectively, ~3 × 1015 cm-3 and ~5 μm. p+/n diodes with not terminated junctions were constructed by a selective area implantation process of 9.2 × 1014 cm-2 Al+ ions at 400°C. The diodes had areas in the range 2×10-4 -1×10-3 cm2. The Al depth profile was 6×1019 cm-3 high and 164 nm thick. The post implantation annealing process was done in a high purity Ar ambient at 1600°C for 30 min. The diode current-voltage characteristics were measured in the temperature range 25-290°C. Statistics of 50-100 measurements per device type were done. The fraction of diodes that could be modeled as abrupt junctions within the frame of the Shockley theory decreased with increasing area value, but was always > 75%. The ideality factor was > 2 only at temperatures > 200°C and bias values < 1 V. The leakage current was extremely weak and remained of the order of 10-9 Acm-2 at 70°C and 500 V reverse bias. 4% of the diodes reached the theoretical voltage breakdown that was 1030 V. The surface roughness of un-implanted and implanted regions after diode processing was, respectively, 2 nm and 12 nm.

Abstract: This paper reports on initial fabrication and electrical characterization of 3C-SiC p+n junction diodes grown on step-free 4H-SiC mesas. Diodes with n-blocking-layer doping ranging from ~ 2 x 1016 cm-3 to ~ 5 x 1017 cm-3 were fabricated and tested. No optimization of junction edge termination or ohmic contacts was employed. Room temperature reverse characteristics of the best devices show excellent low-leakage behavior, below previous 3C-SiC devices produced by other growth techniques, until the onset of a sharp breakdown knee. The resulting estimated breakdown field of 3C-SiC is at least twice the breakdown field of silicon, but is only around half the breakdown field of <0001> 4H-SiC for the doping range studied. Initial high current stressing of 3C diodes at 100 A/cm2 for more than 20 hours resulted in less than 50 mV change in ~ 3 V forward voltage.