The origin of anomalous luminescence efficiency enhancement of short-term aged GaN-based blue light-emitting diodes was studied. We found that the intensity of the electroluminescence and photoluminescence spectra were both increased in the very beginning period of aging. With the help of a rate-equation model, we concluded that this kind of luminescence efficiency enhancement is a joint effect of the defect reduction in active layers and the changes out of active layers, for example the Mg acceptor annealing.

Low dislocation density Ge wafers grown by a vertical gradient freeze (VGF) method used for the fabrication of multi-junction photovoltaic cells (MJC) have been studied by a whole wafer scale measurement of the lattice parameter, X-ray rocking curves, etch pit density (EPD), impurities concentration, minority carrier lifetime and residual stress. Impurity content in the VGF-Ge wafers, including that of B, is quite low although B2O3 encapsulation is used in the growth process. An obvious difference exists across the whole wafer regarding the distribution of etch pit density, lattice parameter, full width at half maximum (FWHM) of the X-ray rocking curve and residual stress measured by Raman spectra. These are in contrast to a reference Ge substrate wafer grown by the Cz method. The influence of the VGF-Ge substrate on the performance of the MJC is analyzed and evaluated by a comparison of the statistical results of cell parameters.

The surface quality of HCl-etched and ammonium sulfide [(NH4)2S]-based treated bulk n-GaSb(100) were compared using x-ray photoelectron spectroscopy (XPS) and TOF-SIMS. It has been found that native oxides present on the GaSb surface are more effectively removed when etched with concentrated HCl solution. With additional [(NH4)2SO4+S] substances or hydrogen ions in the passivation solution, the treated samples displayed significant reduction of native oxides and formation of the sulfides compared with pure (NH4)2S solution. The treated samples also result in a noteworthy improvement in the current–voltage (I–V) characteristics of Au/n-GaSb Schottky contacts, as evidenced by the lower ideality factor (n), higher barrier height (Φb) and higher rectification ratio at ±0.2V. The I–V measurement provided definitive confirmation of XPS and TOF-SIMS results, establishing the need for less alkaline solution for greater passivation stability.

Defects in Sb implanted ZnO single crystals have been studied by using photoluminescence (PL) spectroscopy, X-ray diffraction (XRD) and Raman scattering. Electrical properties of the samples were analyzed by Hall effect measurement. The results indicate that the annealed Sb-implanted sample is n-type with a free electron concentration of the same amplitude as the calculated implantation concentration. The well-known oxygen vacancy related deep level green PL band is suppressed in the as-implanted sample and recovers to the level close to the as-grown ZnO single crystal after annealing. These phenomena suggest that a large portion of as-implanted Sb atoms occupy oxygen lattice site in an unstable state and move to the interstitial site, forming the complex donor defect upon high temperature annealing, resulting in n-type conduction even if the implantation dose is quite high.

The surface chemical properties of gallium antimonide (GaSb) after ammonium sulfide ((NH4)2S) solution passivation have been studied by X-ray photoelectron spectroscopy (XPS), time of flight secondary ion mass spectroscopy (TOF-SIMS) and I–V measurement. An advantage of neutral (NH4)2S + S solution over pure (NH4)2S solution and alkaline (NH4)2S + S solution has been found in the ability to passivate the GaSb surface by contrast and comparison. It has been found that alkaline (NH4)2S + S solution passivation effectively removes oxides of the GaSb surface and forms sulfide products to improve device performance. TOF-SIMS complementally demonstrates that pure (NH4)2S passivation did form sulfide products, which are too soluble to really exist. The lowest roughness determined using a 3D optical profilometer and the highest improved SBD quality proved that neutral (NH4)2S + S solution passivation worked much better in improving the surface properties of GaSb.

Residual impurities and contamination on semi-insulating (SI) InP wafers are detrimental for epitaxial growth and device performance, especially because residual silicon on an SI-InP wafer surface is electrically active and generates an n-type conduction layer at the interface between the epilayer and the InP substrate. In order to reduce the concentration of Si and improve surface quality, the authors investigate a wet-chemical cleaning process for ready-to-use InP substrates. A novel and practical cleaning process was developed by adding an alkaline solution to the conventional acidic cleaning process. Time-of-flight secondary mass spectrometry, a very powerful analysis technique to characterize surfaces and investigate any organic and inorganic contamination present on the InP surface, was used after the samples were etched under different cleaning processes. The results show that the novel etching process effectively reduces the Si contamination.