Degradation modeling of InGaP/GaAs/Ge triple-junction (3J) space solar cells, which are exposed to charged particles (protons and electrons), is introduced using a one-dimensional optical device simulator: PC1D. The proposed method can reproduce the electrical degradation of 3J solar cells from fitting the external quantum efficiencies for subcells. In this modeling, carrier removal rate of base layer $\left(R_C\right)$ and damage coefficient of minority carrier diffusion length $\left(K_L\right)$ in each subcell are considered as radiation degradation parameters. Nonionizing energy loss (NIEL) analysis for both radiation degradation parameters is discussed. The radiation degradation of a 3J solar cell can be predicted from the results of degradation level in the each subcell estimated from correlativity between NIEL and both radiation degradation parameters.

N_CV_Si⁻ centers in SiC [nitrogen-vacancy (NV) centers], which produce near-infrared (NIR) photoluminescence (PL) at room temperature, is expected to have applications as quantum sensors for in vivo imaging and sensing. To realize quantum sensing using NV centers, clarification of the formation mechanism as well as control of the high-density formation is necessary. This paper reports a comprehensive investigation on the NIR-PL properties originating from NV centers in high purity semi-insulating and nitrogen (N) contained 4H-SiC substrates formed by ion beam irradiation and subsequent thermal annealing. It is shown that NV centers are exclusively formed by the contained N as impurities rather than the implanted N, and also the heavier ion irradiations induce the NV center formation effectively than the lighter ion irradiations. The study on thermal annealing at different temperatures reveals that the optimal temperature is 1000 °C. From the results of temperature dependence on the PL intensity, it is shown that little thermal quenching of the PL intensity appears at room temperature and the PL signal is collected even at 783 K. The formation mechanism of NV centers is also discussed based on the obtained results.

We report the enhancement of the optical emission between 850 and 1400 nm of an ensemble of silicon mono-vacancies (V_Si), silicon and carbon divacancies (V_CV_Si), and nitrogen vacancies (N_CV_Si) in an n-type 4H-SiC array of micropillars. The micropillars have a length of ca. 4.5 μm and a diameter of ca. 740 nm, and were implanted with H⁺ ions to produce an ensemble of color centers at a depth of approximately 2 μm. The samples were in part annealed at different temperatures (750 and 900 °C) to selectively produce distinct color centers. For all these color centers we saw an enhancement of the photostable fluorescence emission of at least a factor of 6 using micro-photoluminescence systems. Using custom confocal microscopy setups, we characterized the emission of V_Si measuring an enhancement by up to a factor of 20, and of N_CV_Si with an enhancement up to a factor of 7. The experimental results are supported by finite element method simulations. Our study provides the pathway for device design and fabrication with an integrated ultra-bright ensemble of V_Si and N_CV_Si for in vivo imaging and sensing in the infrared.

We characterized intrinsic deep level defects created in ion collision cascades which were produced by patterned implantation of single accelerated 2.0 MeV He and 600 keV H ions into n -type 4H-SiC epitaxial layers using a fast-scanning reduced-rate ion microbeam. The initial deep level transient spectroscopy measurement performed on as-grown material in the temperature range 150–700 K revealed the presence of only two electron traps, Z _1/2 (0.64 eV) and EH _6/7 (1.84 eV) assigned to the two different charge state transitions of the isolated carbon vacancy, V _C (=/0) and (0/+). C – V measurements of as-implanted samples revealed the increasing free carrier removal with larger ion fluence values, in particular at depth corresponding to a vicinity of the end of an ion range. The first DLTS measurement of as-implanted samples revealed formation of additional deep level defects labelled as ET1 (0.35 eV), ET2 (0.65 eV) and EH3 (1.06 eV) which were clearly distinguished from the presence of isolated carbon vacancies ( Z _1/2 and EH _6/7 defects) in increased concentrations after implantations either by He or H ions. Repeated C – V measurements showed that a partial net free-carrier recovery occurred in as-implanted samples upon the low-temperature annealing following the first DLTS measurement. The second DLTS measurement revealed the almost complete removal of ET2 defect and the partial removal of EH3 defect, while the concentrations of Z _1/2 and EH _6/7 defects increased, due to the low temperature annealing up to 700 K accomplished during the first temperature scan. We concluded that the ET2 and EH3 defects: (i) act as majority carrier removal traps, (ii) exhibit a low thermal stability and (iii) can be related to the simple point-like defects introduced by light ion implantation, namely interstitials and/or complex of interstitials and vacancies in both carbon and silicon sub-lattices.