| Summary: | 博士 === 國立交通大學 === 電子物理系所 === 97 === The interfacial defects properties of GaN-based Schottky diodes have been investigated and fabricated by utilized current voltage temperature (I-V-T) and capacitance-frequency (C-f) methods. Surface states effects of metal-semiconductor-metal (MSM) photodetectors (PDs) and p-i-n PDs is applied high reverse electrical field in illumination to confirm the relationship between ICP-induced defects and optoelectric devices characteristics in this dissertation. The current transport mechanisms are analyzed in terms of specific contact resistance ( ), characteristic energy (E00) and ideality factor (η) under different annealing temperatures. The current transport mechanisms of non-treated n-type GaN was TE and was FE based on the finding that the sample by using ICP etching processes. However, the current transport mechanisms can be changed from FE to TE by annealing at 600℃ in N2 ambient or 500℃ in H2 ambient, that is, the current transport mechanism dominates TE or between TE and FE. These results showed that the ICP damages were reduced to a low level and the Schottky diodes characteristics recovered by annealing 600℃ in N2 ambient or 500℃ in H2 ambient. In this dissertation, we have found that the current transport mechanisms are directly dependent on the surface treated conditions, and annealing processes are an effective step in eliminating these defects, and characterize ICP-induced defects such as s-type, m-type and f-type interfacial defects by capacitance-frequency (C-f) methods. The s-type interfacial defects can be reduced by annealing temperature increasing to 600℃ in N2 ambient or 500℃ in H2 ambient. The m-type interfacial defects can be recovered to non-treated n-type GaN by annealing at high temperature in N2 ambient or in H2 ambient. In f-type interfacial defects, annealing in N2 ambient is more effective than that in H2 ambient. The interfacial defects of the Schottky diode with ICP induced defect is dominant s-type, and non-treated sample is dominant f-type. The interfacial defects is f-type indicating the ICP induced defects nearly recovered to non-treated sample, this is the defects result from epitaxial growth such as dislocation or the others.
On the other hand, the higher responsivity and internal gain for metal semiconductor metal photodetectors (MSM-PDs) with different surface treatment have been fabricated. The responsivity of MSM-PDs with annealing at 400℃, 500℃ and 600℃ in N2 ambient by applying reverse bias -1Volt is 3.95A/W, 0.72A/W and 1.85A/W, respectively. The internal gain of MSM-PDs with annealing at 400℃, 500℃ and 600℃ in N2 ambient at a photon energy of 3.35eV by applying reverse bias -1Volt is 195, 36 and 84, respectively. The higher responsivity and internal gain characteristics for MSM-PDs with ICP etching process and annealing in N2 ambient at different temperatures are clearly observed. This result may attribute to interfacial states such as holes traps what capture or emit electrons or hole as applied high reverse electrical field and illumination. The persistent photoconductivity effects (PPC) in MSM-PDs with interfacial states by annealing treatment have been studied to confirm the ICP-induced defects exist. Photocurrent gradually increased and the dark current decreased with measured time is observed. These results may also attribute to the presence of holes trap or acceptor-type trap states.
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