TY - JOUR
T1 - Luminescence mechanism and carrier dynamic studies of InGaN-based dichromatic light emitting diodes with ultraviolet and blue emissions
AU - Feng, Shih Wei
AU - Tu, Li Wei
AU - Chyi, Jen Inn
AU - Wang, Hsiang Chen
PY - 2008/11/28
Y1 - 2008/11/28
N2 - In this study, to investigate the luminescence mechanism and carrier dynamics of dichromatic InGaN-based light emitting diodes (LEDs) with two active regions, an ultraviolet (UV)-blue LED (UV active region above the blue one) and a blue-UV LED (blue active region above the UV one) were prepared. Photoluminescence (PL), cathodoluminescence (CL), and time-resolved photoluminescence measurements were performed. For the PL spectra of both LEDs, the blue emissions are stronger than the UV emissions. This trend shows that the higher degree of carrier localization of the blue active region, in either the upper or lower portions of the LEDs, can enhance carrier capture and recombination efficiency. Due to the large and bright light spots emitted from indium-rich clusters in the blue active region, CL images showed that the blue emission is dominant in the image shape for both samples. Furthermore, it was shown that the optical properties and carrier dynamics of dichromatic InGaN-based LEDs could be well explained by the combined effects of the carrier localization effect, structures, extraction efficiency, defect density, and carrier capture efficiency in the UV and blue active regions. Also, thermal effect plays an important role in carrier transport behavior in such dichromatic LEDs. The research results provide important information for operation mechanisms and device designs of dichromatic LEDs.
AB - In this study, to investigate the luminescence mechanism and carrier dynamics of dichromatic InGaN-based light emitting diodes (LEDs) with two active regions, an ultraviolet (UV)-blue LED (UV active region above the blue one) and a blue-UV LED (blue active region above the UV one) were prepared. Photoluminescence (PL), cathodoluminescence (CL), and time-resolved photoluminescence measurements were performed. For the PL spectra of both LEDs, the blue emissions are stronger than the UV emissions. This trend shows that the higher degree of carrier localization of the blue active region, in either the upper or lower portions of the LEDs, can enhance carrier capture and recombination efficiency. Due to the large and bright light spots emitted from indium-rich clusters in the blue active region, CL images showed that the blue emission is dominant in the image shape for both samples. Furthermore, it was shown that the optical properties and carrier dynamics of dichromatic InGaN-based LEDs could be well explained by the combined effects of the carrier localization effect, structures, extraction efficiency, defect density, and carrier capture efficiency in the UV and blue active regions. Also, thermal effect plays an important role in carrier transport behavior in such dichromatic LEDs. The research results provide important information for operation mechanisms and device designs of dichromatic LEDs.
KW - Carrier dynamics
KW - Carrier localization
KW - Carrier transport
KW - Cathodoluminescence
KW - Dichromatic light emitting diodes
KW - Extraction efficiency
KW - Time-resolved photoluminescence
KW - White light emitting diodes
UR - http://www.scopus.com/inward/record.url?scp=55249127495&partnerID=8YFLogxK
U2 - 10.1016/j.tsf.2008.09.032
DO - 10.1016/j.tsf.2008.09.032
M3 - 期刊論文
AN - SCOPUS:55249127495
SN - 0040-6090
VL - 517
SP - 909
EP - 915
JO - Thin Solid Films
JF - Thin Solid Films
IS - 2
ER -