| 摘要 |
PURPOSE:To suppress a leak current, which flows through a current confining layer, and a leak current, which is generated due to the absence of the end part of an active layer, by forming a P type layer on an N type InP substrate by a high concentration InGaAsP layer. CONSTITUTION:A compound semiconductor substrate 1 is formed by an N type InP substrate 11 and an N<+> type InGaAsP buffer layer 11'. A P type layer comprising a P<+> InGaP layer is formed thereon. In a layer 12, the carrier concentration, which is higher than that when an InP layer is used, can be obtained by introducing impurities having high concentration. Therefore, the layer 12, i.e., the P layer at the lower side of a current confining layer in a p-n-p-n structure, can be made to be a high concentration layer. In other words, the diffusion length of the carrier becomes short in this region. Even though the carrier flows into the layer 12 from a P type InP layer 5, the diffusion of the carrier can be suppressed. Therefore current confining effect is improved. The growth of an active layer 4 becomes easy, and the problem of leak current flowing in the layer 4 can be solved. |
