Silicon carbide semiconductor device and method of manufacturing silicon carbide semiconductor device
A silicon carbide semiconductor device includes a silicon carbide semiconductor substrate of a first conductivity type, a first semiconductor layer of the first conductivity type, a second semiconductor layer of the first conductivity type, a third semiconductor layer of the first conductivity type, a fourth semiconductor layer of a second conductivity type, first semiconductor regions of the first conductivity type, gate insulating films, gate electrodes, a first electrode, and a second electrode. When a current flows from the first electrode to the second electrode, a peak light emission intensity at a wavelength close to 390 nm is lower than a peak light emission intensity at a wavelength close to 500 nm.
1. A silicon carbide semiconductor device, comprising:
a silicon carbide semiconductor substrate of a first conductivity type, having a first main surface and a second main surface opposite to each other;
a first semiconductor layer of the first conductivity type, provided on the first main surface of the silicon carbide semiconductor substrate, the first semiconductor layer having an impurity concentration lower than an impurity concentration of the silicon carbide semiconductor substrate, the first semiconductor layer having a first surface and a second surface opposite to each other, the second surface facing the silicon carbide semiconductor substrate;
a second semiconductor layer of the first conductivity type, provided on the first surface of the first semiconductor layer, the second semiconductor layer having a first surface and a second surface opposite to each other, the second surface of the second semiconductor layer facing the first semiconductor layer;
a third semiconductor layer of the first conductivity type, provided on the first surface of the second semiconductor layer, the third semiconductor layer having an impurity concentration lower than the impurity concentration of the silicon carbide semiconductor substrate, the third semiconductor layer having a first layer and a second layer on the first layer, the first layer of the third semiconductor layer facing the second semiconductor layer;
a fourth semiconductor layer of a second conductivity type, provided on the second layer of the third semiconductor layer, the fourth semiconductor layer having a first surface and a second surface opposite to each other, the second surface of the fourth semiconductor layer facing the second layer of the third semiconductor layer;
a first semiconductor region of the first conductivity type, selectively provided in the fourth semiconductor layer, at the first surface of in the fourth semiconductor layer;
a gate electrode provided on at least a portion of a surface of the fourth semiconductor layer, between the third semiconductor layer and the first semiconductor region via a gate insulating film;
a first electrode provided on surfaces of the first semiconductor region and the fourth semiconductor layer; and
a second electrode provided on the second main surface of the silicon carbide semiconductor substrate, wherein
a light generated in response to a current flowing from the first electrode to the second electrode has an intensity profile having a first peak and a second peak respectively approximately at 390 nm and 500 nm, and an intensity at the first peak is lower than an intensity at the second peak, and
a portion of the silicon carbide semiconductor substrate, the first semiconductor layer, the second semiconductor layer, and the third semiconductor layer each contain injected protons or helium that introduce point defects, and
the intensity at the first peak is 1/20 or less of the intensity at the second peak.
2. The silicon carbide semiconductor device according to claim 1 , wherein the intensity at the first peak is 1/100 or less of the intensity at the second peak.
3. The silicon carbide semiconductor device according to claim 1 , wherein the first layer of the third semiconductor layer has an impurity concentration lower than an impurity concentration of the second layer of the third semiconductor layer.