Jaroslav Rusnák

Photoluminescence of passivated a-Si:H

. Experimental results relating to evolution of the a-Si:H photoluminescence spectra are presented. The investigated samples were prepared by deposition of thin a-Si:H layer on glass substrate. In the a-Si:H surface region very thin oxide layer was prepared by wet chemical oxidation in 40% nitric acid solution. The defect states of amorphous silicon layer and its interface with oxide were passivated in HCN aqueous solutions. The attention was focused on decomposition procedure of photoluminescence spectra observed at 6 K. The results confirm the existence of several structurally different phases inside of the a-Si:H amorphous matrix. PACS: 78.55.-m, 78.55.Qr, 81.05.Gc

On formation of thin SiO2/a-Si:H interface when biased oxidized semiconductor surface interacts with plasma or liquid solution

In this paper we present the results of research into a relation(s) between the bias voltage of an oxide/a-Si:H/c-Si sample during formation of very-thin and thin oxides and the resulting distribution of oxide/semiconductor interface states in the a-Si:H band gap. Two oxygen plasma sources were used for the first time in our laboratories for formation of oxide layers on a-Si:H: i) inductively coupled plasma in connection with its application at plasma anodic oxidation; ii) rf plasma as the source of positive oxygen ions for the plasma immersion ion implantation process. The oxide growth on a-Si:H during plasma anodization is also simply described theoretically. Properties of plasmatic structures are compared to ones treated by chemical oxidation that uses 68 wt% nitric acid aqueous solutions. We have confirmed that three parameters of the oxide growth process — kinetic energy of interacting particles, UV-VIS-NIR light emitted by plasma sources, and bias of the samples — determine the distribution of defect states at both the oxide/a-Si:H interface and the volume of the a-Si:H layer, respectively. Additionally, a bias of the sample applied during the oxide growth process has a similar impact on the distribution of defect states as it can be observed during the bias-annealing of similar MOS structure outside of the plasma reactor.

On similar electrical, optical and structural properties of MOS structures prepared on a-Si:H/c-Si, porous silicon/c-Si, and c-Si

The paper presents results of research of similar electrical, optical and structural properties of three types of MOS structures prepared on different Si-based semiconductors. Electrical interface properties are investigated by institutionally produced equipment with Charge Version of Deep Level Transient Spectroscopy and time domain C-V. X-ray diffraction at grazing incidence angles is applied to control their structural properties. Optical properties of selected structures are investigated by photoluminescence measurements at liquid helium temperature (approx. 6K in cryostat). Dominant interest is focused on analysis of both electrical properties of MOS porous silicon based structures prepared on p-type crystalline Si and photoluminescence signals of the structures observed around 1.1 eV, respectively. Such parameters as Fermi level position, flat-band voltage, surface potential, position of deep level hole traps, and acceptor density are calculated for various conditions as defined by sample ambient, temperature, and light illumination. Following two main findings are analyzed: i) total suppression of large C-V hysteresis due to suitable illumination and ii) recovering of part of detected interface states in the dark.

Investigation of Deep Interface Traps in Very-Thin Oxide/Si Structures Prepared at Low Temperatures Using Chemical Solutions

An advanced equipment for the charge version of deep level transient spectroscopy (Q-DLTS) and C-V measurements with newly developed software on LabView platform is presented. The ability to record several Q-DLTS behaviors with different rate windows simultaneously is the most important property of the equipment. Q-DLTS with excitation of the MOS structures by low-voltage step and time domain C-V measurements were used to determine interface properties. The contribution presents mainly results obtained on very-thin oxide/n-type crystalline Si structures prepared by oxidation at very low temperatures in nitric acid solutions with various concentrations.