| 摘要 |
PURPOSE:To ensure oscillation by a low threshold current and in a stable lateral mode, by providing current-narrowing channel elements above and below an active layer respectively so as to reduce the expansion of a current. CONSTITUTION:A second current-narrowing channel element 20 is provided on the lower side of an active layer 3 in addition to an internal (first) current-narrowing channel element 12a provided on the upper side of the active layer 3, and said channel element 20 is formed of an inverted mesa portion provided as a stripe-shaped projection 21 in a part of an N-GaAs substrate 1 by etching. The inverted mesa portion 21 of the substrate 1 and a lower clad layer have the same N-conductivity type, while the conductivity type of a second current- narrowing layer 23 is a P type. When a bias is impressed between a P-side electrode 13 and an N-side electrode 14 to make a semiconductor laser operate, a verse bias is caused thereby between the second current-narrowing layer 23 and the lower clad laywr 2, and therefore no current flows across an interface between them. Accordingly, a current flows through a channel from the P-side electrode 13 to the N-side electrode 14 and through a first current-narrowing portion 11 and a second current-narrowing portion 24, and only a current passage passing through the first current-narrowing portion 11 and the second current- narrowing portion 24 is selected. Consequently, efficient concentration of current is effected in a part of the active layer immediately below the first channel element 12a formed of the first current-narrowing layer 10. |
