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A quantitative full‐fitting analysis of photoreflectance (PR) spectra in the region of the fundamental energy gap E0 from MBE n‐GaAs layer structures (n = 5 × 1015 to 1017 cm−3) on n‐GaAs is performed. They exhibit a complex spectral behaviour consisting of Franz‐Keldysh oscillations, and excitonic structure near E0, and for high‐energetic interference oscillations (LEIO). Spectra are measured using pump beam wavelengths of 488 and 633 nm with modulation frequencies between 167 Hz and 1.42 kHz and pump power densities from 2 × 10−3 to 2 W/cm2. Amplitudes and lineshapes of the three components are shown to vary strongly with changes in the excitation conditions and the phase of the synchronously detected signal which allows to investigate the effect of partial modulation and temporal behaviour of the field modulation mechanisms.

Defects in the emitter region of Ga0.51In0.49P/GaAs heterojunction bipolar transistors (HBTs) were investigated by means of deep-level transient spectroscopy. Both annealed (635 °C, 5 min) and as grown metalorganic chemical vapor deposition epitaxial wafers were investigated in this study, with an electron trap observed in the HBT emitter space-charge region from both wafers. The deep-level activation energy was determined to be 0.87±0.05 eV below the conduction band, the capture cross section 3×10−14 cm2 and the defect density of the order of 1014 cm−3. This defect was also found to be localized at the emitter–base interface.

We present an improved photoreflectance (PR) spectroscopy technique upon the prior art in providing a rapid acquisition method of the PR spectrum in a simultaneous and multiplexed manner. Rapid PR (RPR) application is the on-line monitoring of strained silicon. Shrinkage in the silicon bandgap is measured and converted to strain, using theoretical models. Experimental RPR results are in good correlation with Raman spectroscopy.