Gan-based Msm Ultraviolet Detectors

GaN-based meta1-semiconductor-metal (MSM) structure ultraviolet photodetector has been one of the focuses of interest in recent years for its plane structure, fabrication simplicity, and easy integration. However, the mechanisms of the I-V characteristics under illumination, the photocurrent gain and the strong persistent photoconductivity (PPC) are still unexplained to this day. That's why the quality of the photodetector can't be insured.According to the existing theory, the dark I-V characteristics and the I-V characteristics under illumination are simulated using MATLAB software and MEDICI simulator. According the simulated results, the dark I-V curve is in agreement with the experimental date from literature, but the I-V curve under illumination doesn't fit the experimental date from literature in the insaturation region. Furthermore, the existing theory can't explain the photocurrent gain, so the I-V characteristics under illumination are the keystone of the research work.A model of I-V characteristics under illumination in GaN-based metal- semiconductor -metal photodetectors has been built, using steady-state continuity equations and including the effect of surface states. The predicted result by the model agrees with the experimental date from literature. The current under illumination and the responsivity change sharply with the biased voltage in the insaturation region can be explained by our model. The responsivity equation can be proposed from our model and be used to explain the photocurrent gain.The research of the PPC is another highlight. The effect of the traps in the epitaxial layer is analyzed using the MEDICI simulator and Shockley-Read–Hall model, which indicates the PPC is independent of the traps in the epitaxial layer. On the basis of the recombination model with traps located at a potential barrier and the model of the I-V characteristics under illumination that we have built, the model of the attenuation of the current after illumination is proposed. The model can explain the PPC soundly and indicate that the surface states are the cause of the PPC.According to the model of the I-V characteristics under illumination, the model of...