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Pt/AlGaN Schottky-type UV photodetectors were designed and fabricated. A low-temperature AlGaN interlayer buffer was grown between the AlGaN and GaN film in the diode structure epitaxy to obtain crack-free AlGaN active layers. A comparison was then made of the structural, electrical, and optical characteristics of two different diodes: one with an AlGaN(0.5 ㎛)/n+-GaN(2 ㎚) structure (type 1) and the other with an AlGaN(0.5 ㎛)/AlGaN interlayer(150 )/n+-GaN(3 ㎛) structure(type 2). A crack-free AlGaN film was obtained by the insertion of a low-temperature AlGaN interlayer with an aluminum mole fraction of 26 % into the AlXGa1-XN layer. The fabricated Pt/Al0.33Ga0.67N photodetector had a leakage current of 1 ㎁ for the type 1 diode and 0.1 ㎂ for the type 2 diode at a reverse bias of -5 V. For the photoresponse measurement, the type 2 diode exhibited a cut-off wavelength of 300 ㎚, prominent responsivity of 0.15 A/W at 280 ㎚, and UV-visible extinction ratio of 1.5 104. Accordingly, the Pt/Al0.33Ga0.67N Schottky-type ultraviolet photodetector with an AlGaN interlayer exhibited superior electrical and optical characteristics and improved UV detecting properties.