A highly ordered and damage-free Ge inverted pyramid array structure for broadband antireflection in the mid-infrared

Shin, Sangho; Liao, Yikai; Son, Bongkwon; Zhao, Zhi‐Jun; Jeong, Jun‐Ho; Tan, Chuan Seng; Kim, Munho

doi:10.1039/d1tc01134k

Cited by 14 publications

(14 citation statements)

References 57 publications

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“…Out‐of‐plane periodic electric field was seen for the planar GaAs due to the constructive and destructive interference of the incident and reflective light. [ 45 ] Intensive electric field (i.e., colored regions with red and yellow) was observed in air on top of and in between neighboring nanopillars, then shifted from edge to inside and bottom of the nanopillars with the increasing wavelength from 400 to 800 nm. It indicates that the electric field was effectively coupled into the GaAs nanopillars, leading to enhanced visible light absorption.…”

Section: Resultsmentioning

confidence: 99%

Distinct UV–Visible Responsivity Enhancement of GaAs Photodetectors via Monolithic Integration of Antireflective Nanopillar Structure and UV Absorbing IGZO Layer

Liao

Zheng

Shin

et al. 2022

Advanced Optical Materials

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characteristic with a bandgap energy of ≈1.4 eV. The bandgap energy also enables its usage in visible photodetection. [7,8] In addition, GaAs has exhibited its potentials in the ultraviolet (UV) photodetection due to the high absorption coefficient. [9,10] Nowadays, broadband UV-visible photodetectors exhibit outstanding application potentials in areas such as environment, energy, and imaging. [11] Among various semiconductor materials, GaAs is one of the best candidates for broadband UV-visible photodetection considering the suitable bandgap for visible light detection and high absorption coefficient in UV range.However, two challenges still exist in improving the UV-visible responsivity of GaAs photodetectors: 1) surface reflection loss of incident light and 2) shallow penetration depth of GaAs in UV range. The former issue can be effectively ameliorated by employing various antireflection schemes. Among them, surface texturing such as textured GaAs, [12,13] GaAs nanocones [14,15] and porous GaAs [16][17][18][19] has shown a facile and effective way to achieve a broadband antireflection, compared with a multilayered antireflection coating which requires a precise control of refractive index and thickness of individual layer. [20] Although some of these works on surface texturing demonstrated low UV-visible reflection below 5%, none of them have systematically studied an implication of the textured antireflection layer in GaAs photodetectors and their performance enhancement in a broadband UV-visible range. For example, Namiki et al. [21] fabricated GaAs nanogrooves which exhibited distinctly reduced reflectance from 400 to 1000 nm wavelength. However, this photodetector was only characterized under 532 nm visible illumination and its performance enhancement in a broadband UV-visible range was not reported. In fact, it is challenging to realize the UV performance enhancement in GaAs photodetectors due to the latter issue, i.e., the shallow penetration depth of UV light in GaAs which leads to significant loss of photocarriers by recombination. [22] The surface recombination is expected to be more severe in UV range for antireflective structures due to potential formation of more surface states as traps and recombination centers which are introduced by larger surface areas and fabrication methods such as etching. [12,23] On the other hand, Broadband ultraviolet-visible photodetection has been attracting growing research interests in fields of environment, energy, and imaging. Considering the suitable bandgap and high absorption coefficient, GaAs is one of the best candidates for ultraviolet-visible photodetection. In this work, a monolithic integration strategy of nanopillar antireflective structure and InGaZnO (IGZO) ultraviolet absorbing layer is proposed to enhance the ultraviolet-visible spectral responsivity of GaAs photodetectors. Both nanopillar topography and IGZO layer exhibit antireflective performance, leading to the enhancement of the light absorption and responsivity of the photodetectors. By the comb...

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Section: Resultsmentioning

confidence: 99%

Distinct UV–Visible Responsivity Enhancement of GaAs Photodetectors via Monolithic Integration of Antireflective Nanopillar Structure and UV Absorbing IGZO Layer

Liao

Zheng

Shin

et al. 2022

Advanced Optical Materials

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“…The undercut was induced by longer etching, resulting in the larger inverted pyramid size. 36 The additional etch time caused continuous inverse pyramid structures. The undercutting process is required to form continuous inverted Ge pyramids for low reflectance.…”

Section: Resultsmentioning

confidence: 99%

“…The induced lateral modes change the propagation path of the normal incident light, which results in the light scattering effect. 27,36,38 The reflectance was continuously increased from 7 to 25 mm. Accordingly, the transmittance was 0.90 at 5 mm and it decreased to 0.70 at 25 mm.…”

Section: Resultsmentioning

confidence: 99%

A heavily doped germanium pyramid array for tunable optical antireflection in the broadband mid-infrared range

et al. 2022

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“…Germanium (Ge) is a promising candidate in several technological areas, due to the attractiveness governed by its intrinsic properties [1][2][3][4][5][6][7]. In particular, Ge has a relatively small bandgap, making it an ideal candidate for optoelectronic devices operating in the near-infrared (NIR) region, such as photodiodes and thermophotovoltaic (TPV) devices [5][6][7][8][9]. Nevertheless, planar Ge surfaces suffer from high reflectance (∼40% at 1550 nm) resulting in significant optical loss limiting the performance of Ge-based optoelectronic devices.…”

Section: Introductionmentioning

confidence: 99%

Efficient surface passivation of germanium nanostructures with 1% reflectance

et al. 2023

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Germanium (Ge) is a vital element for applications that operate in near-infrared wavelengths. Recent progress in developing nanostructured Ge surfaces has resulted in > 99 % absorption in a wide wavelength range (300 nm- 1700 nm), promising unprecedented performance for optoelectronic devices. However, excellent optics alone is not enough for most of the devices (e.g. PIN photodiodes and solar cells) but efficient surface passivation is also essential. In this work, we tackle this challenge by applying extensive surface and interface characterization including transmission electron microscopy and X-ray photoelectron spectroscopy, which reveals the limiting factors for surface recombination velocity of the nanostructures. With the help of the obtained results, we develop a surface passivation scheme consisting of atomic-layer-deposited aluminum oxide and sequential chemical treatment. We achieve surface recombination velocity as low as 30 cm/s combined with ~1 % reflectance all the way from ultraviolet to NIR. Finally, we discuss the impact of the achieved results on the performance of Ge-based optoelectronic applications, such as photodetectors and thermophotovoltaic cells.

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A highly ordered and damage-free Ge inverted pyramid array structure for broadband antireflection in the mid-infrared

Abstract: With increasing demand for infrared (IR) photonics and optoelectronics, germanium (Ge) has recently regained attention due to its outstanding optical properties in near infrared (NIR) and mid infrared (MIR) ranges....

Cited by 14 publications

References 57 publications

Distinct UV–Visible Responsivity Enhancement of GaAs Photodetectors via Monolithic Integration of Antireflective Nanopillar Structure and UV Absorbing IGZO Layer

Distinct UV–Visible Responsivity Enhancement of GaAs Photodetectors via Monolithic Integration of Antireflective Nanopillar Structure and UV Absorbing IGZO Layer

A heavily doped germanium pyramid array for tunable optical antireflection in the broadband mid-infrared range

Efficient surface passivation of germanium nanostructures with 1% reflectance

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