Browsing by Author "Chen, Liang-Yi"

Now showing 1 - 5 of 5

Characterizations of low-temperature electroluminescence from ZnO nanowire light-emitting arrays on the p-GaN layer
(2010-12-15)
Lu, Tzu-Chun
;
Ke, Min-Yung
;
Yang, Sheng-Chieh
;
Cheng, Yun-Wei
;
Chen, Liang-Yi
Low-temperature electroluminescence from ZnO nanowire light-emitting arrays is reported. By inserting a thin MgO current blocking layer in between ZnO nanowire and p-GaN, high-purity UV light emission at wavelength 398 nm was obtained. As the temperature is decreased, contrary to the typical GaN-based light emitting diodes, our device shows a decrease of optical output intensity. The results are associated with various carrier tunneling processes and frozen MgO defects. (C) 2010 Optical Society of America
Investigation of Carrier Transient Response of Nanopatterned n-ZnO/a-Si(i)/p(+)-Si Photodiodes
(2010-11-01)
Lin, Pei-Hsuan
;
Chen, Cheng-Pin
;
Hung, Yen-Jen
;
Hsu, Shao-Sun
;
Chen, Liang-Yi
We investigated the carrier transient response of the nanopatterned silicon heterojunction photodiodes using ZnO as the n-type semiconductor. The results show that under the constant light illumination intensity, the planar structure has faster carrier response than the nanopatterned amorphous silicon (intrinsic) (a-Si(i)) diodes. It is attributed to a higher number of generated carriers in the nanostructure (due to the lower surface reflectivity) that increases the probability of collisions. On the other hand, the shortest response time of the device with nanopatterned p(+)-Si suggests that carriers can be effectively transported vertically and horizontally through the p-i(intrinsic)-n structure. Furthermore, the wavelength-dependent rise time is correlated to the different transport distance between electrons and holes at different excited wavelengths.
Investigation of Carrier Transient Response of Nanopatterned n-ZnO/a-Si(i)/p(+)-Si Photodiodes
(2010-11-01)
Lin, Pei-Hsuan
;
Chen, Cheng-Pin
;
Hung, Yen-Jen
;
Hsu, Shao-Sun
;
Chen, Liang-Yi
We investigated the carrier transient response of the nanopatterned silicon heterojunction photodiodes using ZnO as the n-type semiconductor. The results show that under the constant light illumination intensity, the planar structure has faster carrier response than the nanopatterned amorphous silicon (intrinsic) (a-Si(i)) diodes. It is attributed to a higher number of generated carriers in the nanostructure (due to the lower surface reflectivity) that increases the probability of collisions. On the other hand, the shortest response time of the device with nanopatterned p(+)-Si suggests that carriers can be effectively transported vertically and horizontally through the p-i(intrinsic)-n structure. Furthermore, the wavelength-dependent rise time is correlated to the different transport distance between electrons and holes at different excited wavelengths.
Investigation of light absorption properties and acceptance angles of nanopatterned GZO/a-Si/p(+)-Si photodiodes
(2010-05-28)
Chen, Cheng-Pin
;
Lin, Pei-Hsuan
;
Hung, Yen-Jen
;
Hsu, Shao-Shun
;
Chen, Liang-Yi
In this work, n-GZO/a:amorphous-Si(i:intrinsic)/p(+)-Si photodiodes are fabricated. We employed a nanosphere lithographic technique to obtain nanoscale patterns on either the a-Si(i) or p(+)-Si surface. As compared with the planar n-GZO/p(+)-Si diode, the devices with nanopatterned a-Si(i) and nanopatterned p(+)-Si substrates show a 32% and 36.2% enhancement of photoresponsivity. Furthermore, the acceptance angle measurement reveals that the nanostructured photodiodes have larger acceptance angles than the planar structure. It also shows that the device with the nanocone structure has a higher acceptance angle than that with the nanorod structure.
Investigation of low-temperature electroluminescence of InGaN/GaN based nanorod light emitting arrays
(2011-01-28)
Huang, Ying-Yuan
;
Chen, Liang-Yi
;
Chang, Chun-Hsiang
;
Sun, Yu-Hsuan
;
Cheng, Yun-Wei
For InGaN/GaN based nanorod devices using a top-down etching process, the optical output power is affected by non-radiative recombination due to sidewall defects (which decrease light output efficiency) and the mitigated quantum confined Stark effect (QCSE) due to strain relaxation (which increases internal quantum efficiency). Therefore, the exploration of low-temperature optical behaviors of nanorod light emitting diodes (LEDs) will help identify the correlation between these two factors. In this work, low-temperature electroluminescent (EL) spectra of InGaN/GaN nanorod arrays were explored and compared with those of planar LEDs. The nanorod LED exhibits a much higher optical output percentage increase when the temperature decreases. The increase is mainly attributed to the increased carriers in the quantum wells for radiative recombination. Also, due to a better spatial overlap of electrons and holes in the quantum wells, the increased number of carriers can be more efficiently recombined in the nanorod device. Next, while the nanorod array shows nearly constant peak energy in the EL spectra at various injection currents at the temperature of 300 K, a blue shift has been observed at 190 K. The results suggest that with less non-radiative recombination and thus more carriers in the quantum wells, carrier screening and band filling still prevail in the partially strain relaxed nanorods. Moreover, when the temperature drops to 77 K, the blue shift of both nanorod and planar devices disappears and the optical output power decreases since there are fewer carriers in the quantum wells for radiative recombination.