This manuscript provides an overview of power semiconductor devices (PSDs) for distributed energy resource (DER) system. To begin with an overview on electrically-triggered SiC and GaN devices followed by a brief narration of ultra-wide-bandgap (UWBG) PSDs. Subsequently, an overview of optically-activated PSDs encompassing photoconductive semiconductor switch (PCSS) and optical bipolar PSDs are provided. Finally, an overview of PSD packaging and reliability is captured.

We present iron-doped beta gallium oxide (Fe- $\beta $ Ga $_{{\text{2}}}$ O $_{{\text{3}}}$ ) as a candidate for photoconductive semiconductor switches (PCSSs) with sub-bandgap light. From a commercially available Fe- $\beta $ Ga $_{{\text{2}}}$ O $_{{\text{3}}}$ wafer, we first did material characterization. This included measurements of absorption coefficient and dopant composition, carrier activation energy up to 200 $^{\circ}$ C, break down field of planar electrodes (limited from material passivation), and free carrier recombination lifetime, and thermal effects up to 203 $^{\circ}$ C on photocurrent with a 447 nm light emitting diode (LED) source. We then demonstrated pulsed operation of a Fe- $\beta $ Ga $_{\text{2}}$ O $_{\text{3}}$ PCSS under different sub-bandgap wavelengths (355, 532, and 1064 nm) and sub-ns pulses. Fe- $\beta $ Ga $_{\text{2}}$ O $_{\text{3}}$ is a candidate for high temperature PCSS with 355 nm responsivity of 7 $\times$ 10 $^{-\text{7}}$ A-cm/W-kV at room temperature and up to 5.5 $\times$ 10 $^{-\text{4}}$ A-cm/W-kV at 200 $^{\circ}$ C. From these investigations, we discuss a simple trap model to describe the illumination process of the PCSS. Fe- $\beta $ Ga $_{\text{2}}$ O $_{\text{3}}$ has a high breakdown field and has moderate responsivity characteristics, but the dark current at high temperature leads to low photo-to-dark current ratio (PDCR). Regardless, we verify its potential as a PCSS material for harsh environment applications.

In this paper, we focus on the physical modeling of the nonlinear operation of intrinsic photoconductive semiconductor switches (PCSS) based on 4H-SiC using coupled electrical and optical simulations to provide performance bounds of the switch as a function of material and geometry parameters, as well as applied bias. We also conduct a full design-space exploration to identify the optimal operating and design conditions to maximize the compound metric fopPout, where fop is the maximum operating frequency, and Pout is the maximum output power the switch can provide. We quantify that a 10-μm long and 5-μm thick 4H-SiC PCSS can deliver output power density greater than 2W/mm at 150 GHz when triggered by a 0.325-μm laser with intensity of 3 kW/cm. The output power density can be significantly enhanced by increasing the optical generation rate as well as by using thicker SiC to improve its absoprtion characteristics. A brief discussion of signal distortion and electrostatic screening effects at high optical bias is included. Finally, we present an analytic model of charge cloud propagation and the frequency of operation based on the physics, material parameters, and geometry of the PCSS. The model accurately captures fop of 4H-SiC PCSS over a broad range of laser spot size, device length, and electrical bias applied at the contacts.

Photoconductive semiconductor switching (PCSS) devices have unique characteristics to address the growing need for electrically isolated, optically gated, picosecond-scale jitter devices capable of operating at high voltage, current, and frequency. The state of the art in material selection, doping, triggering, and system integration in PCSSs is presented. The material properties and doping considerations of GaN, GaAs, SiC, diamond, and β-Ga₂O₃ in the fabrication of PCSS devices are discussed. A review of the current understanding of the physics of the high-gain mode known as lock-on is presented.

Carrier-transport mechanisms are studied in high-purity diamond irradiated with 6 MeV electrons in the dose range of 10¹²–10¹⁶ cm⁻² and annealed at different temperatures up to 1450 °C. Lifetimes and diffusion coefficients are extracted using two pump–probe techniques based on free-carrier absorption and transient-grating principles and then correlated with the corresponding defect evolution from spectroscopic measurements. The neutral monovacancy is revealed as the main carrier recombination center in the as-irradiated diamond, providing bipolar carrier lifetimes of a few nanoseconds at the highest irradiation dose. Carrier-capture cross sections are reduced during annealing as vacancies aggregate into divacancies at ≤1000 °C and extended vacancy clusters at 1450 °C.