| 摘要 |
PURPOSE:To further decrease leaked current by forming a first buried layer in contact with the side of a clad layer so that the conductivity type of the side of the clad layer is reversed to the p-type by solid-phase diffusion of the dopant in the first buried layer. CONSTITUTION:A mesa stripe 20 having an n-type InP clad layer 14 formed on an InGaAsP active layer 13 is formed on a p-type InP substrate 11. On each of the opposite sides of the mesa stripe 20, there are deposited a first buried layer of p-type InP 15A, a second buried layer of p-type InP, a third buried layer of n-type InP and a fourth buried layer of p-type InP subsequently in that order. Said first buried layer 15A has a dopant concentration higher than that of the clad layer 14 and a thickness smaller than that of a second buried layer 15, while the second buried layer. 15 has a dopant concentration lower than that of the first buried layer 15A. The first buried layer 15A is deposited in contact with the side of the clad layer 14, so that the conductivity type of the side region of the clad layer 14 is reversed to the p-type by solid- phase diffusion of the dopant in the first buried layer 15A. Since the region having the conductivity type reversed to the p-type is produced by the solid-phase diffusion, a highly resistive region having an extremely low carrier concentration is produced at the junction between said p-type region and the n-type region. Thereby, leaking current A can be decreased substantially. |
