Abstract: A semiconductor laser includes an anode region of a first conductivity type made of a highly doped region, an active layer adjacent the anode region, a channel region made of a high-resistivity region and adjacent the active layer, a cathode region of a second conductivity type at one end of the channel region which is made of a highly doped region, and a gate region that surrounds at least part of said channel region and which is made of a highly doped region of the first conductivity type. The anode region and channel region have a wider band gap than that of the active layer.