本論文利用光激螢光光譜及拉曼光譜分析AlGaN/GaN異質結構HEMT的光學特性，主要工作分為以下幾個部分。 利用光激螢光光譜判斷2DEG所輻射螢光位置，利用PL能量的位置定性推得兩樣品的內建電場相對大小。利用PR的KFO現象求得樣品內部內建極化電場大小。本實驗使用之樣品的內建電場大小約為457 kV/cm與590 kV/cm。以PR求得的內建電場大小，利用三角位能井的計算，推得兩樣品2DEG輻射在PL光譜上會位移1.1 meV。另由拉曼光譜中計算出樣品所受應力大小，其結果支持由2DEG螢光計算出的內建極化場大小強度關係。 黃光缺陷帶螢光強度與GaN帶邊螢光強度的比值對元件電子特性的影響在本文中被討論，本論文利用縱向缺陷分布檢測方法來檢測樣品的缺陷分布情形。推測漏電流被表面缺陷主導。 變溫光激螢光光譜中發現樣品螢光能量隨溫度變化在低溫下有S型消長，經由Eliseev model擬合得到樣品的局域態能量寬度（σ）約為10 meV。 由變功率光激螢光光譜探討樣品內部載子的發光機制，GaN帶邊輻射主要為帶到帶結合，而黃光缺陷帶主要是為歐傑結合。 最後對樣品表面覆蓋層參雜Mg，成為P-type覆蓋層，目的是對表面進行優化。表面優化情形可以透過深度檢測的量測得到驗證。 ;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.
