Patent ID: 7208774

Claim:
A semiconductor optical device comprising: a first conductive type semiconductor region provided on a surface of GaAs, the first conductive type semiconductor region having a first semiconductor portion and a second semiconductor portion, the first semiconductor portion having a first region and a second region, the second semiconductor portion having a pair of sides, the second semiconductor portion being provided on the first region of the first semiconductor portion; an active layer provided on the second semiconductor portion of the first conductive type semiconductor region, the active layer having a pair of sides; and a second conductive type semiconductor region provided on the sides and top of the active layer, the sides of the second semiconductor portion, and the second region of the first semiconductor portion of the first conductive type semiconductor region, a bandgap energy of the first conductive type semiconductor region being greater than that of the active layer, a bandgap energy of the second conductive type semiconductor region being greater than that of the active layer, the second region of the first semiconductor portion of the first conductive type semiconductor region and the second conductive type semiconductor region constituting a pn junction.