Exposure dependence of the developed depth in nonadiabatic photolithography using visible optical near fields

Kawazoe, Tadashi; Ohtsu, Motoichi; Inao, Yasuhisa; Kuroda, Ryou

doi:10.1117/1.2833587

Cited by 24 publications

(8 citation statements)

References 15 publications

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“…The two-step transition process described above, referred to as a phonon-assisted process, has already been applied to photochemical vapor deposition [6], photolithography [7], photoetching [8], optical frequency up-conversion [9], photovoltaic devices [10], and so on.…”

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confidence: 99%

Si homojunction structured near-infrared laser based on a phonon-assisted process

et al. 2012

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We fabricated several near-infrared Si laser devices (wavelength ∼1300 nm) showing continuous-wave oscillation at room temperature by using a phonon-assisted process induced by dressed photons. Their optical resonators were formed of ridge waveguides with a width of 10 µm and a thickness of 2 µm, with two cleaved facets, and the resonator lengths were 250-1000 µm. The oscillation threshold currents of these Si lasers were 50-60 mA. From near-field and far-field images of the optical radiation pattern, we observed the high directivity which is characteristic of a laser beam. Typical values of the threshold current density for laser oscillation, the ratio of powers in the TE polarization and TM polarization during oscillation, the optical output power at a current of 60 mA, and the external differential quantum efficiency were 1.1-2.0 kA/cm 2 , 8:1, 50 µW, and 1 %, respectively.Because silicon (Si) is an indirect-transition-type semiconductor, it is difficult to use it as a material for optical devices To solve these problems, in the research described here, we developed a Si laser showing continuous-wave operation at room temperature. To do so, we applied the same fabrication method and operating principle used for a Si-LED that we previously developed, which used a Si crystal having a p-n homojunction [4]. We report the results here.Similar to the fabrication of Si LEDs that we have already reported, in this work, first we formed a p-n homojunction by introducing a p dopant into an n-type Si substrate by ion implantation. Then, while irradiating the structure with light, we applied an electrical current to generate Joule heating, causing annealing. Stimulated emission was produced via a two-step transition process driven by the light irradiation. This process is described below [4,5].(i) First step: Dressed photons are generated by the light irradiation in regions where the dopant concentration in the p-n junction has a non-uniform spatial distribution. A dressed photon is a quasi-particle representing a coupled state due to the mutual interaction between a photon and an electron on the nanometer scale. The dressed photon then couples with a multi-mode phonon, generating stimulated emission that causes a conduction-band electron to transition from an initial state |E ex ; el ⊗ |E ex thermal ; phonon to an intermediate state |E g ; el ⊗ |E ex ; phonon . Here, |E ex ; el and |E g ; el respectively represent the excited state (conduction band) and ground state (valence band) of the

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Si homojunction structured near-infrared laser based on a phonon-assisted process

et al. 2012

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“…The operating principle of the Si-PD fabricated in this research is based on a phonon-assisted process caused by dressed photons [16][17][18][19][20]. A dressed photon is a quasiparticle representing a coupled state between a photon and an electron at the nanoscale.…”

Section: Operating Principlementioning

confidence: 99%

“…Therefore, the Si-PD can exhibit photosensitivity even for infrared light with a photon energy smaller than E g . This principle has already been applied to photochemical vapor deposition [16], photovoltaic devices [17], photolithography [18], subnanometer polishing of a glass surface [19], optical frequency up-conversion [20], and other applications.…”

Section: Operating Principlementioning

confidence: 99%

“…[14] and Fig. 1 Because a phonon is involved in the above excitation of the electron, this excitation process is known as a phononassisted process [16][17][18][19][20]. When light having a photon energy smaller than E g is incident on the Si-PD, electrons are excited by the two-step excitation described above, generating a photocurrent.…”

Section: Operating Principlementioning

confidence: 99%

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Increasing Si photodetector photosensitivity in near-infrared region and manifestation of optical amplification by dressed photons

2012

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We fabricated a novel photodetector by subjecting a Si crystal having a p-n homojunction to phononassisted annealing. The photosensitivity of this device for incident light having a wavelength of 1.16 µm or greater was about three times higher than that of a reference Si-PIN photodiode. The photosensitivity was increased for incident light with a wavelength of 1.32 µm by applying a forward current. When the forward current density was 9 A/cm 2 , a photosensitivity of 0.10 A/W was achieved. This value is at least 4000 times higher than the zero-bias photosensitivity. This remarkable increase was due to the manifestation of optical amplification cause by the forward current injection. For a forward current density of 9 A/cm 2 , the small-signal gain coefficient of the optical amplification was 2.2 × 10 −2 , and the saturation power was 7.1 × 10 2 mW.

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“…This annealing method has already been applied to Si, an indirect-transition semiconductor, to realize high-efficiency p-n homojunction-structured LEDs using bulk Si crystal [16]. Also, processing methods based on the same principle have been applied to organic thin-film photovoltaic devices [17], frequency up-conversion via organic dye grains [18], photolithography [19], and subnanometer polishing of glass surfaces [20].…”

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Homojunction-structured ZnO light-emitting diodes fabricated by dressed-photon assisted annealing

2012

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We formed a p-n homojunction by implanting nitrogen ions, serving as a p-type dopant, into an n-type ZnO crystal. A forward bias current was injected into the crystal while irradiating it with light, bringing about Joule heating which annealed the crystal and changed the spatial distribution of the N-dopant concentration. This activated the N-dopant, causing its concentration distribution to be modified in a self-organized manner so as to be suitable for generating dressed photons. A light-emitting diode fabricated by this dressed-photon assisted annealing method showed electroluminescence at room temperature. In a device fabricated by annealing under irradiation with 407 nmwavelength light, at a forward bias current of 20 mA, the peak wavelength of the electroluminescence was 436 nm, the optical output power was 6.2 µW, and the external quantum efficiency was 1.1 × 10 −4 . The emission spectral profile depended on transitions from intermediate phonon states.

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Exposure dependence of the developed depth in nonadiabatic photolithography using visible optical near fields

Cited by 24 publications

References 15 publications

Si homojunction structured near-infrared laser based on a phonon-assisted process

Si homojunction structured near-infrared laser based on a phonon-assisted process

Increasing Si photodetector photosensitivity in near-infrared region and manifestation of optical amplification by dressed photons

Homojunction-structured ZnO light-emitting diodes fabricated by dressed-photon assisted annealing

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