應力調變下氮化銦鎵/氮化鎵量子井之光學特性研究

Abstract

大部份的研究都認為壓電極化現象對氮化銦鎵材料的發光行為有著重大的影響，所以在討論氮化銦鎵/氮化鎵結構的發光機制時，必須仔細考慮到極化場的影響。因此本研究將利用壓電材料外加應力於量子井上，藉由拉曼光譜、光致激發螢光光譜來觀察樣品在外加應力下，壓電場變化情況。由實驗結果顯示，當量子井晶格受到擠壓，氮化鎵和氮化銦鎵隨應力的變化，峰質能量產生相反方向的移動，且壓電場對能帶造成的影響大於能帶間隙的改變量。利用薛丁格方程式的理論計算，分析載子在量子井中波函數的分布及基態能量。並透過理論分析之結果，針對各種可能造成本研究中實驗值和理論計算差異的變異情形進行討論。

The strain-induced piezoelectric polarization in InGaN materials system causes the significant influence in the optical transition energy through much scientific research. This is the essential study of polarization effect in InGaN/GaN heterostructures. In our work, we demonstrate the strain tuning devices to study the polarization fields in InGaN/GaN quantum wells (QWs) heterostructures by applying an external stress using piezoelectric materials. It is necessary to calibrate the strain induced by a piezoelectric actuator with the observed shift of the luminescence and Raman signal. The luminescence peak energy of GaN and InGaN show opposite shift with the applied compressive stress, and the shift in the InGaN PL peak energy under external biaxial compressive stress can be mainly attributed to the increasing in the piezoelectric field. The wavefunctions and transition energy were calculated by solving the one-dimensional Schrödinger equation. We have also compared and discussed the structural parameters or piezoelectric constants of QWs.