OBSERVATION OF STRAIN-INDUCED SPLITTING OF DEGENERATE VALENCE BANDS USING ANGLE-RESOLVED PHOTOEMISSION SPECTROSCOPY

We report the observation of strain-induced splitting of degenerate valence bands at the GAMMA point in coherently strained Ge(100) layers using angle-resolved photoemission spectroscopy. Strain was supplied via pseudomorphic epitaxial growth of Ge films on well-ordered InP(100) substrates: the inherent lattice mismatch between the two semiconductors resulted in a 3.9% tensile biaxial strain in the Ge epilayers. A surfactant layer was employed to increase the critical layer thickness and film quality so that measurements could be made on high-quality, fully strained films. A comparison is made between experimental results and the theoretical predictions of a heterojunction band-offset theory developed by Van de Walle and Martin which incorporates strain.