TY - JOUR
T1 - Electrical, spectral and optical performance of yellow-green and amber micro-pixelated InGaN light-emitting diodes
AU - Gong, Zheng
AU - Liu, N.Y.
AU - Tao, Y.B.
AU - Massoubre, David
AU - Xie, E.Y
AU - Hu, X.D.
AU - Chen, Z.Z.
AU - Zhang, G.Y.
AU - Pan, Y.B.
AU - Hao, M.S.
AU - Watson, Ian
AU - Gu, Erdan
AU - Dawson, Martin
PY - 2012/1
Y1 - 2012/1
N2 - Micro-pixelated InGaN LED arrays operating at 560 and 600 nm, respectively, are demonstrated for what the authors believe to be the first time. Such devices offer applications in areas including bioinstrumentation, visible light communications and optoelectronic tweezers. The devices reported are based on new epitaxial structures, retaining conventional (0 0 0 1) orientation, but incorporating electron reservoir layers which enhance the efficiency of radiative combination in the active regions. A measured output optical power density up to 8 W cm−2 (4.4 W cm−2) has been achieved from a representative pixel of the yellow–green (amber) LED array, substantially higher than that from conventional broad-area reference LEDs fabricated from the same wafer material. Furthermore, these micro-LEDs can sustain a high current density, up to 4.5 kA cm−2, before thermal rollover. A significant blueshift of the emission wavelength with increasing injection current is observed, however. This blueshift saturates at 45 nm (50 nm) for the yellow–green (amber) LED array, and numerical simulations have been used to gain insight into the responsible mechanisms in this microstructured format of device. In the relatively low-current-density regime (<3.5 kA cm−2) the blueshift is attributable to both the screening of the piezoelectric field by the injected carriers and the band-filling effect, whereas in the high-current regime, it is mainly due to band-filling. Further development of the epitaxial wafer material is expected to improve the current-dependent spectral stability.
AB - Micro-pixelated InGaN LED arrays operating at 560 and 600 nm, respectively, are demonstrated for what the authors believe to be the first time. Such devices offer applications in areas including bioinstrumentation, visible light communications and optoelectronic tweezers. The devices reported are based on new epitaxial structures, retaining conventional (0 0 0 1) orientation, but incorporating electron reservoir layers which enhance the efficiency of radiative combination in the active regions. A measured output optical power density up to 8 W cm−2 (4.4 W cm−2) has been achieved from a representative pixel of the yellow–green (amber) LED array, substantially higher than that from conventional broad-area reference LEDs fabricated from the same wafer material. Furthermore, these micro-LEDs can sustain a high current density, up to 4.5 kA cm−2, before thermal rollover. A significant blueshift of the emission wavelength with increasing injection current is observed, however. This blueshift saturates at 45 nm (50 nm) for the yellow–green (amber) LED array, and numerical simulations have been used to gain insight into the responsible mechanisms in this microstructured format of device. In the relatively low-current-density regime (<3.5 kA cm−2) the blueshift is attributable to both the screening of the piezoelectric field by the injected carriers and the band-filling effect, whereas in the high-current regime, it is mainly due to band-filling. Further development of the epitaxial wafer material is expected to improve the current-dependent spectral stability.
KW - photonics
KW - optics
KW - InGaN light-emitting diodes
UR - http://www.scopus.com/inward/record.url?scp=84855444569&partnerID=8YFLogxK
U2 - 10.1088/0268-1242/27/1/015003
DO - 10.1088/0268-1242/27/1/015003
M3 - Article
SN - 0268-1242
VL - 27
JO - Semiconductor Science and Technology
JF - Semiconductor Science and Technology
IS - 1
M1 - 015003
ER -