成長在鍺基板及砷化鎵基板之有序排列磷化銦鎵光學特性研究

Abstract

本論文研究以有機金屬化學氣相沉積法成長於鍺基板以及砷化鎵基板的有序排列磷化銦鎵之光學特性。第一部分探討成長於鍺基板的磷化銦鎵光激螢光結果出現雙波峰(同時出現不同能量之螢光訊號)的原因，我們利用蝕刻配合低溫與室溫光激螢光頻譜以及室溫微光譜拉曼散射量測，證明不同能量的光激螢光訊號來自磊晶層上層與下層有序排列程度不同引起。另外，我們也同時在室溫光激螢光頻譜中發現深層放光(deep level transition)的現象，推測是由於基板的鍺原子擴散至磊晶層取代三族原子後與三族空缺(vacancy)合成化合物而形成深層缺陷所導致。 我們經由室溫的光激螢光頻譜與X光繞射頻譜以理論公式計算出樣品的有序排列程度。並由分別代表隨機排列及有序排列對稱的T_d及C_3v拉曼選擇定律中，選擇只有純C_3v變化影響之特定極化Z(x^' x^')Z ‾與Z(y^' y^')Z ‾方向之拉曼量測觀察到GaP-like LO強度與InP-like LO強度比值與樣品有序排列程度呈現正比關係。 我們選定有序排列程度最高的樣品，由其TED繞射圖訂出樣品有序排列的方向沿著[11 ‾1]方向。以其結果結合極化拉曼頻譜觀察到當雷射極化方向與有序排列方向位於同一平面時，354 cm-1之強度最強。而雷射極化方向與有序排列方向垂直時354 cm-1消失，說明此新模態確實與有序排列相關。

This thesis investigate the optical characteristics of ordered InGaP/Ge and InGaP/GaAs grown by metal-organic chemical vapor epitaxy.In the first part we discuss the origins of dual PL peak in the InGaP/Ge by etching the half of the sample and measuring PL spectroscopy and Raman scattering. We indicate that the different energy PL peaks are attributed to different degree of order in the upper and lower epilayer. The difference of degree of order in epilayer is due to Ge diffusion from the substrate into the InGaP at the heterointerface between the two materials. In addition, we also observe the broaden deep level transitions in room temperature PL spectrums because of the Ge-based complex defeat within the InGaP near the InGaP/Ge heterointerface. In the second part, the degree of order of every samples has been calculated by using band gap determined from room temperature PL and the lattice mismatched determined from XRD. From the Raman selection rule of zinblende structure(T_d symmetry)presents the random InGaP alloy and Cu-Pt structure(C_3v symmetry) presents the ordered InGaP, we choose the specific Raman polarization configuration, Z(x^' x^')Z ‾ and Z(y^' y^')Z ‾, which only varied by C_3v characteristics and are independent on the T_d characteristics. The well correlations are observed between the degree of order and intensity ratio of GaP-like LO mode and InP-like LO mode in Z(x^' x^')Z ‾ and Z(y^' y^')Z ‾ polarization configurations. We confirm the ordering direction of the highest degree of order sample along the [11 ‾1] direction by TED pattern. From the Raman scattering spectrum of the highest sample we observe that the extra Raman mode 354 cm-1 induced by the ordering effect vanish while the polarization of incident laser are perpendicular to the ordering direction and strengthen while the polarization of incident laser lie in the same plane with ordering direction. This indicate that the extra Raman mode relate to the ordering structure.