Variation Of Photoluminescence Research Articles

Photoluminescence study of radiative transitions in ZnTe bulk crystals

This paper focuses on photoluminescence (PL) and selective photoluminescence (SPL) of ZnTe bulk crystals grown by the cold traveling heater method. The crystals exhibit a PL response with a much more intense excitonic zone than the one due to free-to-bound and donor–acceptor bands, denoting a good sample quality. In particular, we have investigated the Y 1 and Y 2 peaks which, in epitaxial layers, have usually been associated with structural defects. On bulk samples they have not been detected so far because of different masked mechanisms. SPL measurements show that the electrons are the most likely involved carriers for this emission. Additionally, the analysis of the PL variation with temperature for the Y 2 peak yields a thermal activation energy of 36 meV. This activation energy and the involved carriers support the fact that these peaks and those appearing at the same energy in epitaxial layers are due to different mechanisms. Finally an emission band in the range of 625–680 nm is analyzed and compared with other results previously reported in the low-energy region.

Improvement of optical properties of gas source MBE grown [formula omitted] short period superlattices

Optical properties of ( GaP) m ( AlP) n normal and (GaP) m 1 (AlP) n 1 (GaP) m 2 (AlP) n 2 ( m = m 1 + m 2, n = n 1 + n 2, m 1 ≥ m 2, n 1 ≥ n 2) modulated superlattices (SLs) grown by gas source molecular beam epitaxy are studied. Optical properties of the normal SLs are improved with increasing growth temperature. The highest photoluminescence (PL) intensity and the narrowest full width at half maximum (9 meV) are obtained for 640°C growth. It is found that the PL intensity variation with measuring temperature is slower for the 640°C grown SLs than for the 600°C grown SLs. Modulated SLs show strong dependence of the PL intensity and wavelength on the modulated SL structure. The PL intensity of the ( m 1 + n 1 = odd, m 2 + n 2 = odd) modulated SLs shows slower temperature variation than that of the normal SLs. At 30 K, the PL intensity of the (9, 4)(4, 3) modulated SL is 2500 times stronger than that of the (13, 7) normal SL. Electroluminescence (EL) emission was measured at 130–300 K for preliminary fabricated light emitting diodes having a GaP AlP (9, 4)(4, 3) modulated SL as the active layer. The temperature variations of PL and EL wavelengths confirm that the EL emission originates from the GaP AlP modulated SL active layer.

Effect of Laser Illumination on Oxidization of Porous Silicon

ABSTRACTWe have studied the effect of laser illumination (argon laser line of 488 nm) on the oxidization process of the inner surfaces of porous silicon (PS) by measuring the photoluminescence (PL), Fourier-transform infrared (FTIR) absorption and x-ray photoelectron spectroscope and contrasted the variations of PL and FTIR spectra of the PS treated in the following four ways: 1. In vacuum with laser illumination (LI) with power density of 12 mW / mm2. 2. In oxygen with LI. 3. In oxygen without LI. The times for all the above three treatments were 1 h. 4. Storage in air for 2 months without LI. The PL peak of PS showed serious degradation and a blue shift in case 2 but only a moderate degradation and no shift in case 1. The results of FTIR absorption show that the LI in an atmosphere of oxygen enhanced greatly the increase of oxygen-related absorption bands and the decrease of various silicon-hydrogen vibrational mode absorption bands.