不同週期數的週期性氮化鎵奈米孔洞層所形成分散式布拉格反射器的反射與散射行為

Abstract

在本研究中，我們透過電化學蝕刻（electrochemical etching, 簡稱ECE）製程製備了六種具有不同週期數多孔洞層的分散式布拉格反射器（distributed Bragg reflector, 簡稱DBR）結構，其反射波段分別位於約 450 和 700 奈米，用來研究其反射與散射行為。所採用的 ECE 施加電壓為 10、11、12 和 13 伏特，目的是產生不同孔隙率，進而導致不同的反射與散射特性。研究發現，當施加較低電壓時，所形成的多孔洞層為單行孔洞結構；而在較高電壓下，則形成多行孔洞結構。在三種不同週期的 DBR 樣品中，反射率通常隨著 DBR 週期增加而提升，然而散射強度則隨著 DBR 週期的增加而下降。在反射波段分別約為 450與 700 奈米的兩組樣品中，700 奈米樣品的散射損耗較低。這種變化趨勢與較長波長情況下散射較弱的普遍理論相符。然而，散射行為也受到孔洞結構的影響。

In this research we prepare six porous-layer-based distributed Bragg reflector (DBR) structures of different periods with the reflection bands around 450 and 700 nm in wavelength through electrochemical etching (ECE) process to study their reflection and scattering behaviors. The ECE applied voltages at 10, 11, 12, and 13 V are chosen to achieve different porosities and hence different reflection/scattering behaviors. It is found that with a lower applied voltage, a porous layer consists of a one-line pore structure. However, at a high voltage, a porous layer is composed of a multiple-line pore structure. Among the three samples of different DBR periods, the reflectance generally increases with increasing DBR period. However, the scattering intensity decreases with increasing DBR period. Between sample series with reflection bands around 450 and 700 nm, the scattering loss in the sample series of 700 nm is lower. This variation trend is consistent with the general theory of weaker scattering at a longer wavelength. However, the scattering behavior also depends on the pore structure.