4H-SiC PiN Research Articles

Deep Level Transient Spectroscopy (DLTS) Study of 4H-SiC Schottky Diodes and PiN Diodes

We have studied capacitance mode Deep Level Transient Spectroscopy (DLTS) of five 4H-SiC Schottky diode and PiN diode designs. Comparing with previous DLTS studies, we have identified four traps levels, Z1/2, EH1, EH3 and EH5. Additionally, a new trap level, EH1, is prominent in blanket Al+ and B+ high-energy implanted samples but less so in mask-implanted samples. Al+ implantation increases EH3 (associated with silicon vacancy) and EH5, while B+ implantation significantly reduces EH3. The Z1/2 peak (associated with carbon vacancy) is reduced to very low levels after B+ and Al+ implantation.

The Cryogenic Testing and Characterisation of SiC Diodes

High-resolution cryogenic performance testing is carried out on 4H-SiC PiN and Schottky diodes. At 2K intervals from 20 to 320K, current-voltage tests are performed to extract static characteristics such as turn-on, ideality factor and barrier height from across the temperature range. We also analyse the performance of the diodes within a low current/voltage switching circuit across the same temperature range using an inductive switching setup. Both diodes suffer markedly increased conduction losses at the lower temperatures, the PiN diode losing all the benefits of conductivity modulation as dopant freezes-out, reducing its series resistance. However, minor gains in the total switching losses are expected at low temperature due to faster switching speeds.

Characterization and Comparison of 4H-SiC(1120) and 4H-SiC(0001) 8° Off-Axis Substrates and Homoepitaxial Films

AbstractHomoepitaxial films of 4H-SiC(1120) and 8° off-axis 4H-SiC(0001) have been grown and characterized. The number of domains and the range of full-width half-maxima values of the x-ray rocking curves of the [1120]-oriented wafers were smaller than the analogous values acquired from the (0001) materials. Hydrogen etching of the former surface for 5 and 30 minutes reduced the RMS roughness from 0.52 nm to 0.48 nm and to 0.28 nm, respectively; the RMS roughness for a 30 μm (1120) film was 0.52 nm. Micropipes in the substrates did not thread beyond the film-substrate interface. The separation distance between stacking faults was determined to be 10 μm by transmission electron microscopy. Hall mobilities and carrier concentrations of 12,200 cm2/Vs and 3.1×1014 cm−3 and 800 cm2/Vs and 7.4×1014 cm−3 were measured at 100°K and 300°K, respectively. Photoluminescence indicated high purity. 4H-SiC(1120) PiN devices exhibited average blocking voltages to 1344 V and a minimum average forward voltage drop of 3.94 V.