Influence of structure on external efficiency of wide stripe semiconductor lasers based on the analysis of spontaneous emission

An analysis of the carrier loss mechanisms in stripe (10-50 μm) contact lasers based on three quantum wells emitting at 780-nm is carried out. The carrier leakage by lateral current spreading and the carrier overflow to the barrier regions are tracked using measurements of the spontaneous emission collected to the side of and normal to the junction plane. The measurements are carried out for two different residual thickness of the p-side cladding region. The residual thickness, along with the stripe width, is a significant factor in determining the overall laser performance. Around 45% of the carriers injected can be lost by lateral current spreading above the threshold in the shallow etched devices. Deeper etching of the p-side cladding layer reduced this loss to 15%. Significant clamping of the carriers above the threshold in the wells under the injection stripe is measured in all structures. An additional increase in the threshold current density is measured for the shallow-etched 10 μm wide stripe lasers over that expected from scaling the wider stripe lasers. This is accounted for lateral current spreading resulting in a wide lasing width and a carrier density profile inducing anti-guiding effects. This results in double-lobed far fields for these lasers.