Mustafa Anutgan

Electroforming of Amorphous Silicon Nitride Heterojunction

The deposition parameters of doped hydrogenated nanocrystalline silicon grown by plasma-enhanced chemical vapor deposition were scanned to obtain highly conductive films. The optimized p+ and n+ nc-Si:H films were used as injecting layers in the fabrication of Si-rich hydrogenated amorphous silicon nitride (a-SiNx:H)-based heterojunction p+in+ diode. The as-grown diode was subjected to a Joule-heating-assisted forming process (FP) via the application of a high electric field. The modifications in the luminescent, electrical, and structural properties of the diode subsequent to the FP were investigated. Although the energy distribution of electroluminescence remains almost the same when compared with that of the fresh diode, its intensity is enhanced by at least 30 times with an orange-red emission easily perceived by the naked eye. Parallelly, the low field-current density drastically increases, presumably due to the Si-nanocrystallite formation within the a-SiNx:H layer. This formation, triggered by the neighboring nanocrystalline-doped layers, was confirmed by the X-ray diffraction measurements indicating the rise in the local temperature during FP.

pin

A plasma enhanced chemical vapor-deposited (PECVD) boron nitride (BN) film on p-type crystalline silicon (p-c-Si) was used to fabricate the metal–insulator–semiconductor (MIS) test structure. The effects of positive (inverting type) and negative (accumulating type) bias stresses on the MIS (Al/BN/p-Si/Al) structure were investigated as a function of time, bias voltage stresses and temperature. Charge injection into the gate dielectric (BN film in this case) was considered as a mechanism to provoke the instability problem that manifested itself as a slow shift of specific voltage (ΔVHH) which symbolizes the whole capacitance–gate bias voltage (C–V) curve. Moreover, the evolution of this shift is followed by monitoring ΔVHH as a function of time, temperature and gate voltage stress and fitted to a functional form for the ΔVHH shift kinetics. Good agreement with the experimental data confirms the charge injection hypothesis behind the shift in C–V curves. Finally, the origin of an eventual defective structure, required by the actual instability, is argued in terms of possible chemical composition of the film. Seemingly BN possesses a turbostratic structure; the first layer at the initial stage in growth is amorphous (even self-doped by a contamination from the underlying silicon substrate) on which a more ordered phase might continue.

Visible Light Emitter

We report the transformation of an ordinary hydrogenated amorphous silicon nitride based heterojunction diode into a strong visible light emitting electroluminescent device. This forming process (FP) comprises Joule heating induced crystallization during the application of sufficiently high forward bias to the fresh diode. FP starts at an arbitrary point and continues until the accompanying visible light is uniformly emitted from the whole diode. This remarkable phenomenon is presented by real-time photography of the lateral propagation of the formed region. Finally, both the role of window electrode for a successful FP and the luminescence mechanism after FP are briefly discussed.

Instability phenomenon originated from the disordered layer of the plasma-deposited BN film/c-Si interface assessed through the MIS structure by admittance measurement

Abstract Hydrogenated amorphous silicon nitride-based heterojunction pin diode was electroformed under sufficiently high forward bias stress leading to its instant nanocrystallization at room temperature. In order to investigate the origin of the accompanying bright visible light emission, current-voltage and electroluminescence (EL) characteristics of the electroformed diode were scanned over temperature. Electrical transport mechanism was analysed in the low, medium and high electric field regimes. Temperature and field dependence of thermal activation energy were discussed. EL characteristics were studied using the spectral energy distribution and the injection current dependence of its intensity. Thermal quenching data of EL and photoluminescence intensities were compared. Finally, the relationship between the electrical transport and luminescence phenomena was attempted to be interpreted within the frame of a self-consistent model.

Bright Visible Light Extraction from Amorphous Silicon Nitride Heterojunction Pin Diode

The anomalous capacitance-frequency (C-f) behavior of hydrogenated amorphous silicon (a-Si:H) p-i-n diode is studied under different forward bias voltages. Instead of the negative capacitance part of the spectra, the positive part is analyzed, where the traditional charge modulation rather than their transport or their recombination dominates the reactive current. Since the physics of the charge modulation under a particular bias is directly related to the depth and the density of the relevant gap states, the forward bias voltage scanned C-f curves are used to estimate the energy distribution of the density of states within the forbidden gap.

Transport and luminescence phenomena in electroformed silicon nitride-based light emitting diode

The resistive memory switching effect of an electroformed nanocrystal silicon nitride thin film light emitting diode (LED) is demonstrated. For this purpose, current-voltage (I-V) characteristics of the diode were systematically scanned, paying particular attention to the sequence of the measurements. It was found that when the voltage polarity was changed from reverse to forward, the previously measured reverse I-V behavior was remembered until some critical forward bias voltage. Beyond this critical voltage, the I-V curve returns to its original state instantaneously, and light emission switches from the OFF state to the ON state. The kinetics of this switching mechanism was studied for different forward bias stresses by measuring the corresponding time at which the switching occurs. Finally, the switching of resistance and light emission states was discussed via energy band structure of the electroformed LED.

Forward bias capacitance spectroscopy for characterization of semiconductor junctions: Application to a-Si:H p-i-n diode

In this work, analysis of spectra with artificial neural network (ANN) and estimation of glucose concentration from the spectrum is aimed by using near infrared spectroscopy (NIR) method. For this purpose, samples of different concentrations obtained by mixing pure water with glucose monohydrate, which was measured via precision scale, and then NIR spectrum of each sample was extracted. Spectral data and concentration values were transferred to MATLAB platform. ANN analysis was conducted after the required signal processing steps. Experimental results are promising in the determination of glucose concentration of any solution by this method including blood sugar.