TEMPERATURE-INDUCED RESONANT RAMAN-SCATTERING OF MOVPE GROWN ZNSXSE1-X GAAS(100) HETEROSTRUCTURES/

ZnSxSe1-x layers with various nominal compositions between x = 0.05 an d 0.31 grown by low-pressure MOVPE on GaAs(100) were investigated by r esonant Raman scattering in the temperature range from room temperatur e (RT) up to approximately 400 degrees C. After growth the samples wer e transferred into an ultra-high vacuum chamber attached to a Raman se t-up with multi-channel detection, that allows Raman spectra to be mea sured continuously while the sample temperature is increased. Owing to the temperature dependence of the bandgap, strong resonance enhanceme nt of the phonon scattering efficiency is observed at certain temperat ures when the energy of the scattered light equals the gap energy. Und er these conditions first order scattering as well as higher order pro cesses are observed. From the frequency difference of the ZnSe- and Zn S-like longitudinal optical (LO) phonons, which is derived consistentl y from 1st and 2nd order structures, the sulphur content x can be dete rmined with high accuracy. From the resonance maxima for different exc itation energies the bandgap energy at RT as a function of the composi tion x is extrapolated. The strong signals at elevated temperatures ob tained by adjusting the resonance conditions clearly demonstrate the f easibility of applying Raman spectroscopy as an in situ and on line gr owth monitor in the MOVPE process.