Multiplication gain and excess noise factor in 4H-SiC APD

4H-SiC is an attractive material for ultraviolet detection owing to its wide band gap and a matured material technology. This paper reports the mean multiplication gain and excess noise factor with electron- and hole-initiated multiplication of a thin 4H-SiC APDs. The impact ionization coefficients for electron (α) and hole (β) using Monte Carlo method over an electric field ranging from 2000 kV/cm up to 5000 kV/cm are simulated in our work. The results show that β >; α, and the ratio remains large even at very high electric field region. The electric field dependence of the impact ionization coefficients equations have been deduced from our model. Based on these equations, the avalanche breakdown voltage, multiplication gain and excess noise factor at different avalanche width have been investigated by considering the effect of dead space. As the width is increasing, the breakdown voltage and multiplication gain also increases proportionally. We observe a significantly higher multiplication gain for hole- than that of electron-initiated multiplication. The excess noise factor of electron-initiated multiplication is greater than that of hole-initiated due to higher number of feedback carriers. Thus, pure hole injection is necessary in order to ensure low excess noise in 4H-SiC APD owing to the large β >; α.