The Study of AlGaN Metal-Semiconductor-Metal and p-GaN/i-InGaN/n-GaN Photodetectors

• Main Authors: Ming-Hsien Wu, 吳明憲
• Other Authors: Shoou-Jinn Chang
• Format: Others
• Language: en_US
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/48775909533814003253

碩士 === 國立成功大學 === 微電子工程研究所碩博士班 === 94 === Abstract 　　In this thesis, the properties and characteristics investigation of Nitride-based photodetectors which had been grown by metal organic chemical vapor deposition were demonstrated. 　　First, the semi-transparent metal contact, Ni/Au ( 3/6 nm ), was annealed by furnace in oxygen. We observed that the transmittance spectra of the Ni/Au thin film can be improved from 45 % to 52 % at 320 nm. Further, we applied the Ni/Au thin film to fabricate AlGaN metal-semiconductor-metal ( MSM ) ultraviolet ( UV ) photodetectors. From the experiment results, the electrical and optical characteristic for our devices have been improved due to the reduction of the leakage current. Then, AlGaN metal-insulator-semiconductor ( MIS ) UV photodetecors were also fabricated in thesis. The SiO2 insulator was deposited by means of plasma enhanced chemical vapor deposition ( PECVD ). It was found that the devices performance have been improved by inserting the SiO2 layer. With a 5 V bias voltage, the photo-to-dark contrast ratio was 1.47 × 103 for the AlGaN MIS photodetectors. It was also found that the rejections are 1.94 × 103 for AlGaN MIS photodetecor. 　　The AlGaN MSM photodetectors with different low temperature ( LT ) grown cap layer were fabricated to improve the performance. By growing the LT cap layer, the leakage current in AlGaN MSM photodetectors can be effectively eliminated. The Schottky barrier height of AlGaN are 0.718, 0.992 and 0.998 eV for as deposited, LT-GaN and LT-AlGaN devices, respectively. Among these three devices, AlGaN MSM photodetectors with LT-AlGaN cap layer have the largest photo-to-dark contrast ratio around 1.94 × 104. Besides, the flat responsivity characteristic was also be investigated. Following, the recessed AlGaN MSM photodetectors with LT-AlGaN cap layer were fabricated to improve the flat responsivity and the low quantum efficiency originated from the additional absorption by the cap layer. 　　Finally, the p-i-n structure photodetectors with p-GaN layer, n-GaN layer and i-InGaN active layer were fabricated. The Ni catalysts technology was applied in p-GaN layer to enhance ohmic characteristics of p-type layer. Further, a SiN passivation layer was introduced in devices to reduce the leakage current originated from the ICP dry etching damage. Then, the related electrical and optical characteristics will be also measured.