Heat-resistant reflectors for enhanced 850-nm near infrared light-emitting diode efficiency

Lee, Hyung-Joo; Park, Gwang-Hoon; So, Jin-Su; Lee, Choong-Hun; Kim, Jae-Hoon; Kwac, Lee-Ku

doi:10.1016/j.infrared.2021.103879

Cited by 8 publications

(4 citation statements)

References 12 publications

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“…When the current was increased, the reflective TS-IR LED chips showed a relatively lower rate of increase than that of the TS IR-LED chips. This may have been owing to the heat-dissipation effect caused by the metal (reflector/eutectic metal) used in the reflective TS IR-LED [ 16 ]. The output powers of the developed IR-LED chips exhibit different properties in Figure 5 b.…”

Section: Resultsmentioning

confidence: 99%

Improved Optical Efficiency of 850-nm Infrared Light-Emitting Diode with Reflective Transparent Structure

Lee¹,

Park

Kwac

et al. 2023

Micromachines

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This study investigated a reflective transparent structure to improve the optical efficiency of 850 nm infrared light-emitting diodes (IR-LEDs), by effectively enhancing the number of extracted photons emitted from the active region. The reflective transparent structure was fabricated by combining transparent epitaxial and reflective bonding structures. The transparent epitaxial structure was grown by the liquid-phase epitaxy method, which efficiently extracted photons emitted from the active area in IR-LEDs, both in the vertical and horizontal directions. Furthermore, a reflective bonding structure was fabricated using an omnidirectional reflector and a eutectic metal, which efficiently reflected the photons emitted downwards from the active area in an upward direction. To evaluate reflective transparent IR-LED efficiency, a conventional absorbing substrate infrared light-emitting diode (AS IR-LED) and a transparent substrate infrared light-emitting diode (TS IR-LED) were fabricated, and their characteristics were analyzed. Based on the power–current (L-I) evaluation results, the output power (212 mW) of the 850 nm IR-LED with the reflective transparent structure increased by 76% and 26%, relative to those of the AS IR-LED (121 mW) and TS IR-LED (169 mW), respectively. Furthermore, the reflective transparent structure possesses both transparent and reflective properties, as confirmed by photometric and radial theta measurements. Therefore, light photons emitted from the active area of the 850 nm IR-LED were efficiently extracted upward and sideways, because of the reflective transparent structure.

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Section: Resultsmentioning

confidence: 99%

Improved Optical Efficiency of 850-nm Infrared Light-Emitting Diode with Reflective Transparent Structure

Lee¹,

Park

Kwac

et al. 2023

Micromachines

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“…Based on previous studies, it could be assumed that the use of ODR by the wafer bonding process is an effective approach for the remarkable improvement of the light efficiency of LEDs [ 11 , 12 , 13 , 14 ]. Most light photons, which are emitted from the active region to the absorbing substrate, are effectively reflected in either the upper surface or sidewalls by the reflective function of ODR.…”

Section: Introductionmentioning

confidence: 99%

Study on P-AlGaAs/Al/Au Ohmic Contact Characteristics for Improving Optoelectronic Response of Infrared Light-Emitting Device

Lee¹,

Shim

Park

et al. 2023

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The Al/Au alloy was investigated to improve the ohmic characteristic and light efficiency of reflective infrared light-emitting diodes (IR-LEDs). The Al/Au alloy, which was fabricated by combining 10% aluminum and 90% gold, led to considerably improved conductivity on the top layer of p-AlGaAs of the reflective IR-LEDs. In the wafer bond process required for fabricating the reflective IR-LED, the Al/Au alloy, which has filled the hole patterns in Si3N4 film, was used for improving the reflectivity of the Ag reflector and was bonded directly to the top layer of p-AlGaAs on the epitaxial wafer. Based on current-voltage measurements, it was found that the Al/Au alloyed material has a distinct ohmic characteristic pertaining to the p-AlGaAs layer compared with those of the Au/Be alloy material. Therefore, the Al/Au alloy may constitute one of the favored approaches for overcoming the insulative reflective structures of reflective IR-LEDs. For a current density of 200 mA, a lower forward voltage (1.56 V) was observed from the wafer bond IR-LED chip made with the Al/Au alloy; this voltage was remarkably lower in value than that of the conventional chip made with the Au/Be metal (2.29 V). A higher output power (182 mW) was observed from the reflective IR-LEDs made with the Al/Au alloy, thus displaying an increase of 64% compared with those made with the Au/Be alloy (111 mW).

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“…Next, some studies investigated metal reflectors containing single elements (Au, Al, and Ti) and their alloys. [23][24][25] Generally, Au reflectors were widely applied to make high-performance infrared VCSELs. 23,24 However, some research has suggested that Ag might be a better candidate because of its lower cost and higher optical reflectivity in theoretical simulations compared to the case of Au.…”

Section: Introductionmentioning

confidence: 99%

“…23,24 However, some research has suggested that Ag might be a better candidate because of its lower cost and higher optical reflectivity in theoretical simulations compared to the case of Au. [25][26][27] Next, some alloy metals could show higher reflectance compared to Au reflectors. However, the application of alloying metals is sometimes limited due to complex processes, such as multistep deposition and thermal treatment processes, for alloy formation.…”

Section: Introductionmentioning

confidence: 99%

Improved optical efficiency of GaAs-based infrared vertical-cavity surface-emitting laser enabled by combining a metallic reflector and a Bragg reflector

Jang,

Lee,

Kim

et al. 2023

Journal of Vacuum Science &Amp; Technology A

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The use of coupled reflectors was investigated to improve the device performance of GaAs-based 860 nm vertical-cavity surface-emitting lasers (VCSELs). Here, the combined reflector was fabricated by coupling a metallic reflector (Ag) and a distributed Bragg reflector of an epitaxial structure. The performance parameters of the VCSEL, such as light-emitting efficiency, operational voltage, and power consumption, were dramatically improved by using a combined reflector. As a result, infrared GaAs-based VCSELs with combined reflectors could show superior light-emitting performance and reduced operational threshold voltage characteristics compared to conventional VCSELs.

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Heat-resistant reflectors for enhanced 850-nm near infrared light-emitting diode efficiency

Cited by 8 publications

References 12 publications

Improved Optical Efficiency of 850-nm Infrared Light-Emitting Diode with Reflective Transparent Structure

Improved Optical Efficiency of 850-nm Infrared Light-Emitting Diode with Reflective Transparent Structure

Study on P-AlGaAs/Al/Au Ohmic Contact Characteristics for Improving Optoelectronic Response of Infrared Light-Emitting Device

Improved optical efficiency of GaAs-based infrared vertical-cavity surface-emitting laser enabled by combining a metallic reflector and a Bragg reflector

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