Investigation of yellow/green II-VI compound semiconductor laser diode structures on InP substrates

II-VI-compound-semiconductor laser diode (LD) structures on InP substrates were investigated using device simulations and waveguide analysis. Our simulations showed that electron injection from the n-cladding into the active layer is hindered by the n-side barrier layer between the n-cladding and active layer. Consequently, holes are not injected into the active layer but instead leak to the n-side layers. It was shown that carrier injection efficiency can be improved by removing the n-barrier. On the contrary, no large differences were observed between the optical confinement factors of the LD structures with and without the n-barrier layer. In experiments, we have fabricated the LD structures with and without the n-barrier layer on InP substrates using molecular beam epitaxy. The turn-on voltage of the device without the n-barrier was smaller than that for the device with the n-barrier by about 5 V. Spontaneous orange emissions around 603 nm were observed for the devices without the n-barrier. In contrast, no emission was observed for the devices with the n-barrier. These results prove that the carrier injection into the active layer is enhanced by the removal of the n-barrier, leading to improved the device performances.