Optical Properties of AlGaN/GaN HEMT Structure and Its Defect Discussion

• Main Authors: Wei-Hsuan Tseng, 曾偉瑄
• Other Authors: Cheng, Chao-Chia
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/j5u87e

碩士 === 國立中央大學 === 物理學系 === 105 === In this thesis, we have studied the optical properties of AlGaN/GaN HEMT heterostructure by photoluminescence(PL)、Photo-Reflectence(PR) and Raman spectroscopy. PL result shows there is peak corresponding to 2DEG. The band bending by piezoelectric field is approximate to a triangular well. In PR spectra, using the FKO phenomenon calculated the internal electric field are 457 kV/cm and 590 kV/cm. Then put the electric field from PR result into eigen-energy of triangular well to get the 2DEG emission shift is 1.1 meV. The relationships between PL intensity ratio of YL and Band edge and the HEMT electric properties have been discussed in this thesis. We developed a method to identify the vertical defect distribution, and postulate that current leakage is dominated by surface defect. The temperature dependent GaN Band to band PL emission energy exhibited the s-shape shift. Applying the Eliseev model, the fitting result shows the localized energy dispersion is about 10 meV. Carriers recombination mechanism are showed by power dependence PL. As a result, the GaN Band edge is band-to-band recombination and the YL is the auger recombination. In Raman spectra, the strain in sample is calculated. The result of Raman agree to the piezoelectric field calculation by 2DEG emission. Last but not the end, P-type capping layer with Mg dopant can optimize the surface defect, which is supported by the result of vertical defect distribution.