Chang-Feng You

Enhancement of Schottky barrier height on p-type GaN by (NH4)2Sx treatment

Barrier height values of Ni contacts to (NH4)2Sx-treated p-type GaN (p-GaN) were obtained from current-voltage and x-ray photoelectron spectroscopy (XPS) measurements in this study. The induced deep level defect band through high Mg doping led to a reduction of the depletion layer width in the p-GaN near the interface and an increase in the probability of thermionic field emission (TFE). Furthermore, the calculated barrier height value of Ni contacts to (NH4)2Sx-treated p-GaN using the TFE model is close to the Schottky limit, which is in good agreement with the observed result by XPS measurements and suggests that (NH4)2Sx surface treatment leads to the removal of native oxides and the reduction of the surface state related to oxygen-induced and nitrogen-vacancy defects.

Defect-dependent carrier transport behavior of polymer:ZnO composites/electrodeposited CdS/indium tin oxide devices

Currents through the poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) and ZnO nanoparticles (PEDOT:PSS:ZnO)/CdS/indium tin oxide (ITO) hetero-structures are studied. The authors introduced the electrodeposition technique with sulfide treatment to improve the film quality of CdS. It is shown that sulfide treatment leads to a reduction in the number of donor-like defects (that is, sulfur vacancies and cadmium interstitials) in the CdS films, which leads to the conversion of carrier transport behavior from Poole-Frenkel emission to thermionic emission-diffusion for PEDOT:PSS:ZnO/CdS/ITO devices. A correlation is identified for providing a guide to control the current transport behavior of PEDOT:PSS:ZnO/CdS/ITO devices.

Effects of Sulfide Treatment of Indium Tin Oxide on Efficiency of Polymer Light-Emitting Diodes

The effects of the sulfide treatment of indium tin oxide (ITO) on the efficiency of polymer light-emitting diodes (PLEDs) were investigated in this study. We found that an increase in the work function of ITO and a decrease in the number of oxygen vacancies (VO) near the ITO surface region (due to the occupation of VO by sulfur) result in an increase in device efficiency. It is worth noting that a suitable sulfide treatment time is an important issue for producing high-external-quantum-efficiency PLEDs. [DOI: 10.1143/JJAP.46.647]

Mechanisms of Performance Improvement for Polymer Light-Emitting Diodes Fabricated on ( NH4 ) 2S x -Treated Indium-Tin Oxide Substrates

Photoelectron spectroscopy measurements show that (NH 4 ) 2 S x surface treatment may lead to an increase in the work function of indium-tin oxide (ITO), due to the occupation of oxygen vacancies (V O ) by sulfur and a reduction in the amount of V O near the ITO surface region. Comparison between the current-luminance-voltage characteristics of polymer light-emitting diodes fabricated on ITO substrates with and without (NH 4 ) 2 S x treatment, shows that (NH 4 ) 2 S x treatment led to the enhancement of external quantum efficiency, due to the reduction of forward-biased leakage current (resulting from the reduction of V O -related defects near the ITO surface region).