The measurements of luminescence spectra were performed on series of porous silicon (PS) samples, obtained in wide range of anodic etching regimes. Photoluminescence (PL) spectra contain two closely spaced luminescence bands. The energy difference between them ∼0.15–0.2 eV depends very slightly on their spectral position. The ratio of the intensities of the two PL bands is monotonously changing with the changes in sample porosity. Thus, in very porous samples only the short-wavelength band is usually observed, while in slightly porous samples only the long-wavelength band is observed. Interaction of PS samples with water at first produces a small decrease of PL band intensities, and then a new band in the range of 0.7 μm appears, which is presumably related to an oxide layer at the surface of PS nanocrystallites. After treating PS in alcohols, the initial band intensity drops and the long-wavelength band disappears completely in less than 1 min. It is discovered that the presence of water contained in the ethanol (even at a content of ∼1%), leads to emergence of a new intensive PL band in the range of 0.7 μm. In very porous samples or after washing or storage of as-anodized PS in water or alcohols, the long-wavelength band is rarely observed experimentally because its intensity is very small.
The effects of hydrogen treatment on electrical properties, luminescence spectra, and deep traps in InGaAlP and InGaP have been studied. It is shown that acceptors and donors (both shallow and deep) can be effectively passivated by hydrogen. The hydrogen is found not only to passivate the main electron and hole traps in our samples, but also to generate electron traps in n-InGaAlP and hole traps in p-InGaP. The influence of hydrogen treatment mode (direct plasma or a crossed-beams source in which the low-energy ion bombardment of the surface is effectively eliminated) on hydrogen concentration and hydrogen profiles in InGaAlP are discussed.
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