3.1.1. Capacitance–Voltage Characterization

Capacitance–voltage (C–V) measurements were carried out up to 600 V at 25 ◦C, in order to determine the donor-concentration profile of the epitaxial layer (Figure 3a). The detector was placed in a test fixture Agilent 16065A connected to an Agilent 4284A Precision LCR Meter (Santa Clara, CA, USA). A Keithley 2410 voltage source (Cleveland, OH, USA), operating in the four-wire connection mode, was used to bias the device and measure the applied voltage. The measurement was performed with a 100 mV AC signal at 100 kHz. The donor-concentration profile as a function of the depleted layer width was determined from the slope of a 1/C2–V curve, according to [24], see Figure 3a. Please note that the C–V measurements were performed using a 4H-SiC Schottky diode with area *A* = 5 mm2, produced from the same wafer. A full depletion of 124 μm was reached, polarizing the detector up to 600 V (Figure 3b). A mean value of <ND> = (5.20 ± 0.06) × 10<sup>13</sup> cm<sup>−</sup><sup>3</sup> was determined (Figure 4).

**Figure 3.** (**a**) Capacitance–voltage (C–V) and 1/C2–V per unit area characteristics. From the fit curve, the mean value of the donor concentration is expected to be (5.56 ± 0.05) × 10<sup>13</sup> cm<sup>−</sup>3; (**b**) depleted layer and mean electric field as a function of applied voltage, as derived from C–V measurements. The theoretical result is obtained using 5.56 × 10<sup>13</sup> cm<sup>−</sup><sup>3</sup> as the mean value of the doping concentration.

**Figure 4.** Donor concentration profile as a function of the depleted layer width. The full depletion of 124 μm was reached at 600 V. A mean value of <ND> = 5.2 × 10<sup>13</sup> cm<sup>−</sup><sup>3</sup> was determined.

### 3.1.2. Statistical Leakage–Current Distribution

Current–voltage (I–V) measurements were carried out on each of the 32 strips of two different SiC detectors, SM1 and SM3, at room temperature (Figure 5). The two detectors were biased at 100 V and 200 V from the back ohmic contact using a Keithley 2410 source meter, whereas the current of each strip was measured connecting a Keithley 6430 electrometer to the front, rectifying the Schottky contact. The guard electrode surrounding the microstrips was kept to ground to collect the parasitic current generated at the device's chip edges. Figure 5 shows the current and current density values for each of the 32 strips of the two different microstrip detectors as measured at 25 ◦C and 200 V. Such bias voltage generates an inner electric field of about 30 kV/cm. Ultra-low current mean values of 2.2 fA and 7.6 fA were measured for the two microstrips under test, corresponding to current densities of 4.4 pA/cm<sup>2</sup> and 15.2 pA/cm2.

**Figure 5.** Current and current density measured at 25 ◦C and 200 V on the 32 strips of the two microstrip detectors, SM1 and SM3. Current values of few fA (current densities of low pA/cm2) were measured on all strips.
