Photoconductivity and photoluminescence of GaAs grown on Si by molecular beam epitaxy

Abstract Photoconductivity (PC) and photoluminescence (PL) have been used to characterize GaAs grown on Si (100) by molecular beam epitaxy. The GaAs layers are known to be under biaxial tensile strain because of the difference in the thermal expansion coefficients of GaAs and Si. This strain is responsible for the splitting between heavy- and light-hole valence bands and could be monitored via the electron to heavy-hole (e-hh) and electron to light-hole (e-lh) transitions. These two transitions are observed in both PL and PC spectra. The stress present in the GaAs layer is calculated to vary from 1.8 kbar at room temperature to 2.7 kbar at 4.2 K. It is also shown that the temperature evolution of the stress as a function of temperature is entirely controlled by the difference between the thermal expansion coefficients of the two materials.