Enhanced Non-Uniformity Modeling of 4H-SiC Schottky Diode Characteristics over Wide High Temperature and Forward Bias Ranges

A practical model, adequate for full reproduction of inhomogeneous Schottky diodes' forward characteristics over wide high-temperature and bias ranges, is proposed. According to this ${p}$ -diode model, the Schottky contact current is considered to flow through ${m}$ parallel-connected internal diodes, each with stable, constant barrier height and specific series resistance (both main model parameters). The value of ${m}$ , required to reproduce the entire electrical forward behavior of a non-uniform Schottky contact, is directly connected to a particular model parameter ( $p_{eff}$ ), used to define the inhomogeneity degree. The p-diode model was tested on forward characteristics measured for both Ni and commercial Ti Schottky diodes on 4H-SiC, which exhibited varying degrees of inhomogeneity. Excellent replication of experimental curves was achieved for all investigated samples, even those with obvious irregularities, such as 'humps', explained in the model by the series resistances' influence. In the case of m = 1, the proposed model does not produce identical results with the conventional model of a homogeneous Schottky contact if $p_{eff} e 0$. The value of this parameter indicates how much of an inhomogeneous contact's area is essentially used for current conduction

Effects of Excimer Laser Irradiation on the Morphological, Structural, and Electrical Properties of Aluminum-Implanted Silicon Carbide (4H-SiC)

This paper reports on the effects of excimer laser irradiation on an aluminum (Al)-doped silicon carbide (4H-SiC) layer. Specifically, high-concentration (1 × 1020at/cm3) Al-implanted 4H-SiC samples were exposed to a few pulses of 308 nm laser radiation (pulse duration of 160 ns), with fluence varying from 1.0 to 2.8 J/cm2. As a starting point, the laser-induced modifications of the morphological, microstructural, and nanoelectrical properties of the exposed 4H-SiC surface were monitored by combining different techniques. From these investigations, an evolution of the surface morphology was observed that can be ascribed to a conversion during irradiation of the uppermost part of the 4H-SiC implanted layer into a polycrystalline region of 3C-SiC and 6H-SiC grains, surmounted in the order by a crystalline-Si layer and an amorphous C-rich region. Then, the electrical characteristics of the implanted layer were evaluated by means of test structures appropriately fabricated on the samples. The high value of sheet-resistance of the irradiated layer (in the order of 104kω/sq) suggested a poor activation of the p-type dopant and/or a low mobility of the carriers in the polycrystalline 3C-SiC/6H-SiC layer. The outcomes of this study can be useful for a fundamental understanding of laser annealing treatments of 4H-SiC implanted layers, toward a possible use in 4H-SiC technology of this process

Validation of the Italian version of carers’ quality-of-life questionnaire for parkinsonism (PQoL Carer) in progressive supranuclear palsy

Progressive supranuclear palsy (PSP) is a rare, rapidly progressive, neurodegenerative disease characterized by falls and ocular movement disturbances. Caring for a partner or relative who suffers from PSP entails a strenuous and demanding task, usually lasting for years that affects carers’ everyday life routines and emotional and social well-being. The 26-item Parkinsonism Carers QoL (PQoL Carer) is a self-administered, concise instrument evaluating the quality of life of caregivers of patients with atypical parkinsonism (both PSP and multiple system atrophy). Here, the PQoL Carer was translated into Italian and validated in 162 carers of PSP patients (54.3% women; mean age (standard deviation), 62.4 (15.4)) diagnosed according to the Movement Disorder Society criteria and recruited in 16 third-level movement disorders centers participating in the Neurecanet project. The mean PQoL total score was 40.66 ± 19.46. The internal consistency was excellent (Cronbach’s alpha = 0.941); corrected item-total correlation was > 0.40 for all the items. A correlation with other health-related quality of life measures as well as with behavioral assessments was shown suggesting adequate convergent validity of the scale. PQoL also correlated with patients’ severity of disease. The discriminant validity of the scale was evidenced by its capacity to differentiate between carers with varying levels of self-reported health (p < 0.001). In conclusion, the Italian version of the PQoL Carer is an easy, consistent, and valid tool for the assessment of the quality of life in carers of PSP patients

Validation of the Italian version of carers’ quality-of-life questionnaire for parkinsonism (PQoL Carer) in progressive supranuclear palsy

Progressive supranuclear palsy (PSP) is a rare, rapidly progressive, neurodegenerative disease characterized by falls and ocular movement disturbances. Caring for a partner or relative who suffers from PSP entails a strenuous and demanding task, usually lasting for years that affects carers’ everyday life routines and emotional and social well-being. The 26-item Parkinsonism Carers QoL (PQoL Carer) is a self-administered, concise instrument evaluating the quality of life of caregivers of patients with atypical parkinsonism (both PSP and multiple system atrophy). Here, the PQoL Carer was translated into Italian and validated in 162 carers of PSP patients (54.3% women; mean age (standard deviation), 62.4 (15.4)) diagnosed according to the Movement Disorder Society criteria and recruited in 16 third-level movement disorders centers participating in the Neurecanet project. The mean PQoL total score was 40.66 ± 19.46. The internal consistency was excellent (Cronbach’s alpha = 0.941); corrected item-total correlation was &gt; 0.40 for all the items. A correlation with other health-related quality of life measures as well as with behavioral assessments was shown suggesting adequate convergent validity of the scale. PQoL also correlated with patients’ severity of disease. The discriminant validity of the scale was evidenced by its capacity to differentiate between carers with varying levels of self-reported health (p &lt; 0.001). In conclusion, the Italian version of the PQoL Carer is an easy, consistent, and valid tool for the assessment of the quality of life in carers of PSP patients