A thin sample of semiconductor, 2 micrometers thick, is subjected to a laser power of 100 mW/cm^2. The wavelength of the laser is 620 nm. The bandgap of the semiconductor is 1.5 eV. The absorption coefficient a is 1E-4/cm.
i) What is the input photon flux?
ii) What is the absorbed photon flux? The remaining photons go through the material.
iii) Assume that all absorbed photons give rise to electrons and holes, which recombine to give back light. Approximately, at what wavelength will they emit light? This is called photoluminescence. See the section on photoluminescence in Ch.14.
iv) What is the efficiency of photoluminescence, i.e. divide the luminescence power by the input power.