Browsing by Author "Li, Jin-Chai"

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Improved Output Power of InGaN-Based Ultraviolet LEDs Using a Heavily Si-Doped GaN Insertion Layer Technique
(2012-02-01)
Chiu, Ching-Hsueh
;
Lin, Chien-Chung
;
Tu, Po-Min
;
Huang, Shih-Cheng
;
Tu, Chia-Cheng
In this paper, a high quality ultraviolet lightemitting diodes (UV-LEDs) at 375 nm was developed using a heavy Si-doping technique with metal organic chemical vapor deposition. By using high-resolution X-ray diffraction, the full width at half-maximum of the rocking curve shows that the GaN film inserting a heavily Si-doped GaN layer (Si-HDL) had high crystalline quality. From the transmission electron microscopy image, the threading dislocation density was decreased after inserting a Si-HDL between undoped and n-doped GaN layers by nanoscale epitaxial lateral overgrowth. As a result, a much smaller reverse current and a higher light output were achieved. The improvement of light output at an injection current of 20 mA was enhanced by 40%. Therefore, we can use an in-situ nano pattern without complex photolithography and etching process and improve the internal quantum efficiency of UV-LEDs.
Improvement in efficiency droop of GaN-based light-emitting diodes by optimization of active regions
(2012)
Lin, Da-Wei
;
Wang, Chao-Hsun
;
Chang, Shih-Pang
;
Chiu, Ching-Hsueh
;
Lan, Yu-Pin
In this paper, we propose several methods to improve the efficiency droop of GaN-based light-emitting diodes by optimization of active regions, such as alternative substrates, semi-polar MQWs, insertion layer, graded-thickness MQWs, and graded-composition EBL.
Optical and Electrical Properties of GaN-Based Light Emitting Diodes Grown on Micro- and Nano-Scale Patterned Si Substrate
(2011-07-01)
Chiu, Ching-Hsueh
;
Lin, Chien-Chung
;
Deng, Dong-Mei
;
Lin, Da-Wei
;
Li, Jin-Chai
We investigate the optical and electrical characteristics of the GaN-based light emitting diodes (LEDs) grown on micro-and nano-scale patterned silicon substrate (MPLEDs and NPLEDs). The transmission electron microscopy images reveal the suppression of threading dislocation density in InGaN/GaN structure on nano-pattern substrate due to nano-scale epitaxial lateral overgrowth. The plan-view and cross-section cathodo luminescence mappings show less defective and more homogeneous active quantum-well region growth on nano-porous substrates. From temperature-dependent photoluminescence (PL) and low temperature time-resolved PL measurement, NPLEDs have better carrier confinement and higher radiative recombination rate than MPLEDs. In terms of device performance, NPLEDs exhibit smaller electroluminescence peak wavelength blue shift, lower reverse leakage current and decrease in efficiency droop when compared with the MPLEDs. These results suggest the feasibility of using NPSi for the growth of high quality and power LEDs on Si substrates.