In this study, an AlGaInP/GaP-based heterostructure featuring a silicon substrate and a SiO 2 /indium tin oxide/Ag omnidirectional reflector, using a metal-to-metal bonding technique, serves as a dual-function device operating in light emitting and photovoltaic modes. To enhance the light extraction efficiency and conversion efficiency, AlGaInP/Si heterojunction devices with a periodic texture applied to the n-͑Al 0.5 Ga 0.5 ͒ 0.5 In 0.5 P surface layer using photolithography and a wet etching process are also presented. Using the light emitting mode and a 350 mA current injection, the external quantum efficiencies of AlGaInP/Si light emitting diodes ͑LEDs͒ with ͑LED-I͒ and without ͑LED-II͒ a textured surface are measured at approximately 17.3 and 11.8%, respectively. The enhancement of the output power in LED-I can be attributed to a multitude of bowl-shaped notches on the surface, resulting in a reduction in the reabsorption probability of photons inside the device because the photon path length of LED-I is shorter than LED-II before photons escape into free space. When devices are operated in a photovoltaic mode, measured under an air mass 1.5 condition, the typical efficiency and fill factor are around 4.67 and 83%, respectively, for devices with a textured surface.Surface texturing techniques are available and can be customized to improve light extraction and incident efficiency of semiconductor optoelectronic devices, including light emitting diodes ͑LEDs͒ and solar cells. 1,2 In conventional ͑Al x Ga 1−x ͒ 0.5 In 0.5 P LED emitting wavelengths of 560-670 nm, the light extraction efficiency ͑LEE͒ of AlGaInP/GaAs LEDs is low because the downward light is absorbed by the thick GaAs substrate. 1 Although the problem of substrate absorption can be partially resolved by using distributed Bragg reflectors, these only exhibit a narrow band of high reflectivity. 1 AlGaInP LEDs with high levels of brightness, featuring a metal or a Si substrate and a metal reflector layer ͓an omnidirectional reflector ͑ODR͔͒, are thus developed to further enhance the LEE of AlGaInP LEDs. 3 The transparent substrate ͑TS͒-type AlGaInP LEDs using wafer-direct bonding technology have been applied for more than a decade. However, such TS-LEDs require a critical and costly GaP wafer-bonding process. 4 For the so-called metal bonding ͑MB͒ LEDs, 3 the technical requirements are less strict during the device process vs the wafer-direct bonding process. 5 In addition to the absorption of the GaAs substrate, critical angle loss, due to large differences between the high refractive-index semiconductor material and the lower refractive-index surrounding material, i.e., air or resin, is also a crucial issue. To enhance the escape probability of photons generated in the active layer of the LED, a large critical angle or a rough surface is required. 1,6 Although the refractive index of a semiconductor cannot be changed, one can enhance the LEE by roughening the semiconductor surface. For an LED, the angular randomization of photons can be achieved ...
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