Martin Domeij

Time Resolved Gate Oxide Stress of 4H-SiC Planar MOSFETs and NMOS Capacitors

Lateral SiC MOSFETs and NMOS capacitors were fabricated and electrically evaluated for channel mobility, DIT and gate oxide breakdown. Time resolved measurements of VTH and VFB drift during gate bias stress were performed resulting in logarithmic time dependence for moderate stress time and temperature. Gate bias stress was also carried out during 20 hours at temperatures up to 225 C. Stress times resulting in a VTH shift of 500 mV were determined and an activation energy EA=0.86 eV was extracted for the VTH drift.

Stability of Current Gain in SiC BJTs

In this work, large area SiC BJTs with good long-term stability in 1000 hrs DC stress tests are demonstrated. It is also illustrated how wafer scanning techniques can be used to reject BJT dies with basal plane dislocations, thereby eliminating the risk for bipolar degradation.

1200 V, 3.3 mΩ SiC Bipolar Junction Transistor Power Modules

Epoxy moulded power modules with a small footprint of 40 mm x 55 mm were fabricated with two switches, each consisting of six parallel 1200 V 50 A rated BJTs and Schottky diodes. The SiC-based power modules have very low on-resistance of 3.3 mΩ and a current gain of 80, both at room temperature. An inverter with specially designed drive circuits was constructed using the power modules and an efficiency of 98.5 % was shown for an output power of 12 kW.

Detection of crystal defects in high doped epitaxial layers and substrates by photoluminescence

In this work, the detection and characterization of various crystal defects in high doped silicon carbide by photoluminescence (PL) is explored. The detection of basal plane dislocations in high doped epitaxial buffer layers is demonstrated using the near ultraviolet (NUV) spectra. Several characteristic defects in high doped 150mm substrates like grain boundaries and screw dislocations are also detected and characterized using the NUV PL spectra. Further characterization using molten potassium hydroxide etching is presented.