ANALYSIS OF SYNCHRONOUS PHASE, PUMP POWER, AND PUMP WAVELENGTH-DEPENDENT COMPLEX PR SPECTRA FROM GAAS MBE STRUCTURES

A quantitative full-fitting analysis of photoreflectance (PR) spectra in the region of the fundamental energy gap E(0) from MBE n-GaAs layer structures (n = 5 x 10(15) to 10(17) cm(-3)) on n-GaAs is performed. They exhibit a complex spectral behaviour consisting of Franz-Keldysh oscillations, and excitonic structure near E(0), and for high-energeti c interference oscillations (LEIO). Spectra are measured using pump be am wavelengths of 488 and 633 nm with modulation frequencies between 1 67 Hz and 1.42 kHz and pump power densities from 2 x 10(-3) to 2 W/cm( 2). Amplitudes and lineshapes of the three components are shown to var y strongly with changes in the excitation conditions and the phase of the synchronously detected signal which allows to investigate the effe ct of partial modulation and temporal behaviour of the field modulatio n mechanisms.