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Polarized photoluminescence properties of a-plane InGaN/GaN multiple quantum wells
|Authors: ||Yen-Ju Chiu|
|Contributors: ||NTOU:Institute of Optoelectronic Sciences|
polarization;multiple quantum wells;InGaN;GaN;photoluminescence;a-plane
|Issue Date: ||2011-06-22T08:38:20Z
|Abstract: ||本論文以極化光激螢光光譜，研究同時具有侷域能態與二維量子井能態的a面成長氮化銦鎵/氮化鎵多重量子井之發光性質。在E垂直c極化螢光部分，主要的螢光是侷域能態的發光；而E∥c極化螢光部分，則以二維量子井能態（two dimensional quantum well states）的發光為主。隨著銦含量的增加，侷域能態相對於二維量子井能態的發光強度隨之增加。晶格不匹配度導致價帶能階分裂的現象，在侷域能態的發光部分，當銦含量較低時（9%至14%），是可以分辨的；當銦含量較高時（24%至30%），能階分裂的現象變得較不明顯，這是當銦含量較高時，量子井內In的聚集(segregation)區域呈現較無序結晶的狀態，晶格不匹配度對於價帶能階分裂的影響因而降低所致。另一方面，二維量子井能態的發光，晶格不匹配度導致價帶能階的分裂仍隨著銦增加含量而變大。 本論文研究結果顯示，極化光激螢光光譜有利於研究氮化銦鎵/氮化鎵多重量子井中，侷域能態與二維量子井能態的發光機制，以及晶格不匹配度對於發光機制的影響。本論文的研究結果，將有助於發展及設計與極化光相關之氮化銦鎵/氮化鎵多重量子井光電元件。|
This thesis performed the polarized photoluminescence (PL) measurements to study the emission properties of the a-plane In GaxN/GaN multiple quantum wells (MQWs) with both the localized states and the two-dimensional quantum well (2D-QW) states. For the PL, the main luminescence is the emission from the localized states, while for the E∥c PL, the dominant luminescence is the emission from the 2D-QW states. As the In content of the MQWs is increased, the ratio of the intensity of the emission from the localized states relative to that from the 2D-QW states is increased. For the emission from the localized states, the valence band splittings due to the lattice mismatch between the InGaN and GaN layers were found to be discernible for MQWs with lower In content (9%, 14%) and become indistinguishable for MQWs with higher In concent (24%, 30% ). This could be understood by the reduction of the effect of lattice mismatch on the valence splitting due to the disorder at the regions with stronger In segregations. On the other hand, for the emission from the 2D-QW states, the valence band splittings due to the lattice mismatch between the InGaN and GaN layers were found to become pronounced as the increase in the In content of the MQWs. Our results indicate that polarized PL measurements are powerful for the study on the effects of the localized states, the 2D-QW states, as well as the lattice mismatch on the emission properties of the InGaN/GaN MQWs. The research results are helpful for the development and design of the polarized emission related InGaN/GaN MQWs optoelectronic devices.
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