Epitaxial growth and the electronic structure of MgSe on ZnSe/GaAs (001)

We have examined the growth and electronic properties of thin layers of MgS e on relaxed 0.6 mum ZnSe epilayers. This avoids potential complications wh en MgSe is grown directly on GaAs substrates. Using relatively low energy p hotons from the BESSY1 synchrotron radiation facility to enhance the photoe mission cross-sections, we have monitored the evolution of the 3d core leve ls of Zn, and Se together with the 2s and 2p levels of Mg as a function of MgSe layer thickness, using the technique of angle resolved photoemission. By using a substrate temperature of 350 degreesC, we obtained consistently good c(2X2) LEED patterns after each evaporation cycle: the maximum MgSe th ickness investigated was 3.2 nm. From an examination of the energy shift of the substrate Se 3d level following MgSe deposition (attributed to band be nding) and determination of the apparent shift in the position of the valen ce band maximum, we estimate the true value of the valence band offset as - 0.34 eV (relative to ZnSe), Both surface and "bulk" Se contributions have b een identified and an estimate of 0.44 nm for the inelastic mean-free-path of 56 eV electrons in MgSe has been;derived. Normal emission valence band d ata utilizing a wide range of photon energies has been used to determine th e band structure of MgSe (001) for the first time using the usual assumptio ns associated with a free electron final state model. Using an inner potent ial of 9.1 eV we find the binding energies of the X, and X, points to be 1. 5 and 3.85 eV respectively relative to the valence band maximum. (C) 2001 E lsevier Science B.V. All rights reserved.