| 摘要 |
PURPOSE:To enable the photodetector to operate at a high speed by coupling 1st and 2nd optical waveguides optically and inverting the conduction type of a light absorbing layer so that a p-n junction in formed along the 2nd optical waveguide at right angles to a substrate. CONSTITUTION:For example, grooves 21 are formed in stripes on a semi- insulating semiconductor substrate 11 and an n-type optical waveguide layer 12 (1st optical waveguide 14) and an n-type light absorbing layer 13 (2nd optical waveguide 15) are formed by crystal growth having their border at right angles to the grooves 21 so that the surface is flat; and p-type impurities are diffused to part of the light absorbing layer 13 to form a p-n junction along the grooves 21 and a reverse bias is applied between a p-side electrode 18 and an n-side electrode 19. Therefore, the p-n junction 17 is separated electrically by a separation groove 21 except at a necessary part of about 5mum along the 2nd optical waveguide 15. Consequently, more reduction than the area of the p-n junction of a conventional photodetector is attained, the junction capacity becomes extremely small, and the whole capacity is reduced greatly, thereby enabling fast operation. |
