| Summary: | 碩士 === 中原大學 === 電子工程研究所 === 98 === In this thesis, AlN thin film grown on c-sappire using Heclion sputtering system in low temperature(300~500℃)，and in application to fabricated the AlN metal-semiconductor-metal(MSM) photodetector.
There were correlations of AlN thin film crystalline, surface morphology and transmittance characteristic measured by XRD, AFM and photospectrometer. In XRD θ-2θ scan, rocking curve and AFM measurement, AlN(1μm)/sapphire with relatively poor performance compared with AlN(4000Å)/Sapphire. It attributed to the great stress between AlN and Sapphire based on the large lattice mismatch of 12%, the stress effect more serious with thicker film growth. After all, AlN(1μm) still exhibit apparent c-axis preferred-oriention growth on c-sapphire, and low R.M.S roughness about of 1nm. And with low FHWM value in rocking measurement. In transmittance, it found that AlN exhibit high transmission in long wavelength(500~800nm), and decay abruptly in the wavelength of 200nm, it also indicate the great quality of AlN thin film. The best optical bandgap of 6.16 eV which very closed to the theoretical value of AlN Bulk can be calculation from the transmittance spectrum of the AlN thin film which exhibit best transmission with substrate temperature of 450℃
AlN MSM device were fabricated on AlN/Sapphire with the low temperature of 300℃, exhibit a low dark current between 191~795 fA with different electrode spacing. The dark current of the photodetectors in this thesis is closed to the AlN MSM devices fabricated by MOCVD in reported literatures, indicating the excellent quality in the AlN film growth. The photo/dark current ratio of the devices shows almost 2 orders of magnitude with the illumination of D2 lamp, and the relationship between photo current and light power is in good linearity. The peak responsivity of 3.65×10-6 A/W at the wavelength of 200nm and larger about 2 order than the responsivity at wavelength of 400nm, it consisting with the optical bandgap calculation and reveal the good selection ability of wavelength. According to the result, AlN MSM devices are suitable for deep UV detectors.
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