Thin P-type Layer Research Articles

Demonstration and modeling of unipolar-carrier-conduction GaN Schottky-pn junction diode with low turn-on voltage

By introducing a thin p-type layer between the Schottky metal and n-GaN layer, this work presents a Schottky-pn junction diode (SPND) configuration for the GaN rectifier fabrication. Specific unipolar carrier conduction characteristic is demonstrated by the verification of temperature-dependent current–voltage (I–V) tests and electroluminescence spectra. Meanwhile, apparently advantageous forward conduction properties as compared to the pn diode fabricated on the same wafer have been achieved, featuring a lower turn-on voltage of 0.82 V. Together with the analysis model established in the GaN SPND for a wide-range designable turn-on voltage, this work provides an alternative method to the GaN rectifier strategies besides the traditional solution.

A new guard ring for radiation induced noise reduction in photodiodes implemented in 0.18 μm CMOS technology

A new p-type guard ring by introduction of a thin p-type layer which encloses shallow trench isolation (STI) layer is utilized to reduce radiation induced noise in photodiodes implemented in 0.18 $$\upmu$$ m standard complementary-metal-oxide-semiconductor (CMOS) technology. The guard ring efficiency is characterized according to a new radiation model developed for p–n photodiodes implemented in the same technology. The extracted model which is the oxide trapped charges and interface state values is verified using a simulation setup for two different structures. The optimized guard ring with the doping concentration of $$10^{+19}$$ atoms cm $$^{-3}$$ reduces the dark current of photodiodes at 1 Mrad dose of ionizing radiation from $$6.97\,\times \,10^{-13}$$ A (without the guard ring) to $$1.29\,\times \,10^{-14}$$ A for STI in contact with the active region structure and from $$5.95\,\times \,10^{-13}$$ A (without the guard ring) to $$2\,\times \,10^{-14}$$ A for STI surrounded p-well structure. The proposed guard ring can be used as a promising structure for ionizing radiation hardening of photodiodes.

Fabrication and evaluation of plasmonic light-emitting diodes with thin p-type layer and localized Ag particles embedded by ITO

Light-emitting diodes (LEDs) have been demonstrated with a thin p-type layer using the plasmonic effect. Optimal LED device operation was found when using a 20-nm-thick p+-GaN layer. Ag of different thicknesses was deposited on the thin p-type layer and annealed to form the localized Ag particles. The localized Ag particles were embedded by indium tin oxide to form a p-type electrode in the LED structure. By optimization of the plasmonic LED, the significant electroluminescence enhancement was observed when the thickness of Ag was 9.5 nm. Both upward and downward electroluminescence intensities were improved, and the external quantum efficiency was approximately double that of LEDs without the localized Ag particles. The time-resolved photoluminescence (PL) decay time for the LED with the localized Ag particles was shorter than that without the localized Ag particles. The faster PL decay time should cause the increase in internal quantum efficiency by adopting the localized Ag particles. To validate the localized surface plasmon resonance coupling effect, the absorption of the LEDs was investigated experimentally and using simulations.

Comment on “Chen et al., Fabrication and photovoltaic conversion enhancement…”, Electrochimica Acta, 2014

In a recent article, Chen et al. [Electrochimica Acta, 2014, 130: 279] presented their fabrication and characterization results on a graphene/n-Si solar cell where the Au nanoparticles were inserted in graphene to increase its optical and electrical properties. The higher efficiency of the device was attributed to increased conductivity of graphene after doping with Au nanoparticles. However, the knowledge in the field of Schottky diode solar cells relates this to increased band bending at the junction. Also, to explain the instability behaviour, they concluded that the growth of silicon oxide on the Si surface or oxygen adsorption on the window layer resulted in the device performance increasing initially and decreasing in the end. However, this instability seems to be due to variation in series resistance reduced at the beginning because of slightly lowered Fermi level and increased at the end by the self-compensation by deep in-diffusion of Au nanoparticles into n-Si layer. We also propose that inserting a very thin p-type layer at the junction will enhance the carrier collection and performance of this device.

Photoelectrochemical Properties of the p−n Junction in and near the Surface Depletion Region of n-Type GaN

Photoelectrochemical water splitting is expecting a new energy source to produce hydrogen from water. The photoilluminated electrode using a uniform semiconductor single crystal has been well analyzed, but the effect of that using a structural semiconductor is still obscure. The properties of one of the structural semiconductors with a p−n junction in and near a depletion region were investigated using the samples with thin p-type layers on n-type GaN in this article. The properties were also evaluated by the calculation based on the Poisson equation. Not only the band-edge energy of a semiconductor at the semiconductor−electrolyte interface but also the length of the depletion region and the band-edge energy profile affected the photocurrent density from the evaluation. The effect of the energy profile of the depletion region is also discussed.

Photoelectrochemical H2 Gas Generation Improvement with Thin p-Type GaN Layer on n-Type GaN

Existence of a p-n junction in a depletion layer is expected to change band energy distribution. The structures of thin p-type GaN on n-type GaN were investigated for the working electrode of the photoelectrochemical reactions. When the p-type layer thickness was thinner than the depletion layer, lower flatband potential was observed. The photocurrent density and the H2 gas generation also increased when the n-type GaN working electrode with thin p-type layer was used.

Numerical study of barrier height enhancement in n‐In 0.35 Ga 0.65 As Schottky diodes using a p‐type near‐interface layer

We have simulated electrical characteristics of n-type In0.35Ga0.65As Schottky diodes with a thin p-type layer at the surface. By a numerical solution of Poisson and drift-diffusion equations I–V and C–V curves of model structures have been calculated. The diode parameters, such as barrier height and ideality factor and the influence of the p-type layer thickness on them, were evaluated and compared with the published data in literature. The barrier height increases continuously with the thickness of the p-type layer. The worsening of the ideality factor is shown not to be detrimental for the device performance. For greater p-type layer thicknesses, however, the diode ceases to be a majority type device because minority carriers as part of the total current start to increase and the device should no more be considered as a majority type one.

Current induced degradation in boron-doped hydrogenated amorphous silicon: A novel investigation technique

A novel technique for controllable degradation and monitoring of a boron-doped layer as used in thin film solar cells is presented. The thin p-type layer under investigation is grown embedded in a n-i-n structure. Upon biasing the structure, excess electrons are injected into the layer giving rise to a degradation process. Complete recovery after annealing indicates the metastable nature of the process. The degree of degradation can be monitored by following changes of the forward current flowing into the structure. A simple model enables the interpretation of the experimental curves in terms of doping activation and increased density of defects in the doped layer.

1Improvement of Thick a-Si Radiation Detectors by Field Profile Tailoring

ABSTRACTApplication of thick (∼50 μm) a-Si p-i-n diodes as a direct radiation detector for minimum ionizing particles is hampered by the need to apply large bias voltages in order fully to deplete the detecting intrinsic layer, which typically contains 5–10×1014 ionizable dangling bonds per cm3. By insertion of thin p-type layers at intervals within the intrinsic layer, the required depletion voltage can be reduced by a factor of at least 1/(n+1) where n is the number of layers inserted. This principle is demonstrated for devices approximately 12μm in thickness. It is shown that electron losses within the p type layer can be kept to minimum by choice of a low doping concentration for the introduced p layers.

Shallow p-type layers in InP by Hg implantation

Ion implantation of mercury in n-type and semi-insulating indium phosphide is reported in InP. We show how mercury behaves in InP in terms of type of dopant, electrical activity, and diffusivity. Implanted mercury impurity behaves as an acceptor dopant in InP. Thin p-type layers have been obtained. Mercury profiles and electrical profiles show that mercury does not diffuse towards the bulk during annealing; therefore, mercury implantation can be a valuable technique in realizing shallow p-type layers in indium phosphide.

A method for selective substrate removal from thin p-type gallium arsenide layers

A two-stage etching technique enables the substrates to be removed from thin p-type layers of gallium arsenide over large areas. An n-type 'blocking layer' is used to retard the etching front during the selective first stage and this is subsequently removed using a nonselective etch. Greater precision is offered by this method than by conventional etching techniques.

Transient photovoltaic response of diffused-junction silicon photodiodes

The results of an experimental and theoretical study of the transient photovoltaic response of diffused-junction silicon photodiodes are presented. The analysis pertains to a thin p-type layer diffused in an n-type wafer illuminated on the p-type surface. According to an exact solution for the transient response of the photocurrent at the junction, the rise time is limited by minority-carrier storage. Expressions for the external photovoltage rise and fall times indicate that in general the rise time at room temperature with no external bias depends on the light intensity as well as the load resistance, while the fall time depends only on the load resistance. Previous attempts by others to show experimental agreement with theory have not been completely satisfactory. Some experimental difficulties have been overcome by using an extremely fast light chopper. Rise and fall time measurements made on a silicon photodiode (TI Type LS 222) are in very good agreement with analysis. Impedance measurements which are important in showing the effect of load resistance on rise time are also discussed.