Slight contaminations existing in a material lead to substantial defects in applied paint. Herein, we propose a strategy to convert this nuisance to a technologically useful process by using an azobenzene-containing side chain liquid crystalline (SCLCP) polymer. This method allows for a developer-free phototriggered surface fabrication. The mass migration is initiated by UV-light irradiation and directed by super-inkjet printed patterns using another polymer on the SCLCP film surface. UV irradiation results in a liquid crystal-to-isotropic phase transition, and this phase change immediately initiates a mass migration to form crater or trench structures due to the surface tension instability known as Marangoni flow. The transferred volume of the film reaches approximately 440-fold that of the polymer ink, and therefore, the printed ink pattern acts as a latent image towards the amplification of surface morphing. This printing-aided photoprocess for surface inscription is expected to provide a new platform of polymer microfabrication.
By using a transparent conductive oxide (TCO) gate for the short-wave infrared (SWIR) region, the high optical responsivity of 180 A/W at 1550 nm and the broadband photosensitivity up to 1800 nm are demonstrated in InGaAs photo field-effect transistors (photoFETs) with front-side illumination (FSI). The photoresponse of the InGaAs photoFETs through the TCO gate can be reasonably explained by the photovoltaic effect in the photoFET operation. It was found that the spectral responsivity characteristics of TCO gate InGaAs photoFETs exhibit higher and broader responsivity compared with those of the InGaAs photodiode. The TCO gate InGaAs photoFETs are the most promising architecture for a high responsivity and broadband SWIR FSI photodetector for monolithic integration with optical communication devices and Si-LSI.
InGaAs photo field‐effect transistor (photoFET) on Si is the most promising candidate for a high responsivity shortwave infrared (SWIR) photodetector toward monolithic integration with Si‐LSI. To evaluate spectral responsivity characteristics of front‐side illumination (FSI) InGaAs photoFETs integrated on Si wafer, the photocurrent measurement system with a wide area SWIR illumination is developed. This allows us to extract more accurate incident power density illuminating on the whole sensing area. From the incident power dependence of the responsivity, the spectral responsivity characteristics at a constant incident power are derived. It is found that the spectral responsivity characteristics of InGaAs photoFETs on Si present higher and broader responsivity than that of InGaAs photodiode.
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