以週期性之氮化鎵奈米孔洞層形成分散式布拉格反射器的反射與散射行為

Abstract

我們設計並製造四組基於氮化鎵多孔結構的分佈式布拉格反射器樣品，用於比較其鏡面反射、直線穿透和散射行為，其反射帶中心波長範圍從450至1500奈米不等。在每組樣品中，採用了四種不同的電化學蝕刻電壓以研究不同蝕刻條件的影響。為了實現更長的分散式布拉格反射器工作波長，使用具有較厚的高矽摻雜氮化鎵層的分散式布拉格反射器結構，使孔洞的數量或尺寸變大，導致更強的散射。因此，較長工作波長的分散式布拉格反射器並不一定會帶來更低的散射損耗。此外，我們還比較了有檯面及無檯面製作的分散式布拉格反射器結構及其性能。未進行檯面製作時，薄多孔層的孔隙率較低，導致較低的反射率以及更強的散射，反之，厚多孔層的孔隙率較高，導致較高的反射率以及更的散射。

Four series of GaN porous-structure based distributed Bragg reflector (DBR) samples with different central wavelengths of reflection bands for comparing their specular reflection, line-of-sight transmission, and scattering behaviors are designed and fabricated with the central wavelengths of reflection bands ranged from 450 to 1500 nm. In each series of sample, four electrochemical etching voltages are used for comparing the results of different etching conditions. With a thicker highly Si-doped GaN layer for achieving a longer DBR operating wavelength, the pore number is higher and/or the pore size is larger in such a DBR structure, leading to strong scattering. Therefore, a DBR of a longer operating wavelength does not necessarily lead to a smaller scattering loss. The structures and performances of the DBRs with and without mesa fabrication are also compared. Without mesa fabrication, the porosity is lower (higher) in a thin (thick) porous layer leading to lower (higher) reflectivity and stronger (weaker) scattering.