Realization of GaxIn1-xAszP1-z/Gay In1-yAszP1-z-superlattices with abrupt interfaces for optoelectronics at λ=1.55 μm

Semiconductor superlattices attract the interest of physicists as well as of engineers since their electronic and optical properties are affected by externally applied voltages e.g. for optical switching devices. For sufficiently high structural quality periodicity induced effects like the Wannier-Stark effect occur. However, strain balanced superlattices do not operate in the technologically important wavelength region at 1550 nm. In this paper, we describe the addition of phosphorous into the material system as an approach to overcome this problem. This should allow one to increase the band gap of the well and barrier without changing other structural parameters like strain and period length. Photoluminescence results indicate that fluctuations of the quaternary composition and/or layer thickness are responsible for the reduced quality of these superlattices. We discuss how these effects can be avoided by optimization of growth parameters such as total reactor pressure and temperature. Finally, we present photocurrent results for optimized structures with abrupt interfaces showing the Wannier-Stark effect