Influence Of Surface Recombination Research Articles

The role of surface states and point defects on optical properties of InGaN/GaN multi-quantum wells in nanowires grown by molecular beam epitaxy

The optical properties of nanowire-based InGaN/GaN multiple quantum wells (MQWs) heterostructures grown by plasma-assisted molecular beam epitaxy are investigated. The beneficial effect of an InGaN underlayer grown below the active region is demonstrated and assigned to the trapping of point defects transferred from the pseudo-template to the active region. The influence of surface recombination is also investigated. For low InN molar fraction value, we demonstrate that AlO x deposition efficiently passivate the surface. By contrast, for large InN molar fraction, the increase of volume non-radiative recombination, which we assign to the formation of additional point defects during the growth of the heterostructure dominates surface recombination. The inhomogeneous luminescence of single nanowires at the nanoscale, namely a luminescent ring surrounding a less luminescent centre part points towards an inhomogeneous spatial distribution of the non-radiative recombination center tentatively identified as intrinsic point defects created during the MQWs growth. These results can contribute to improve the performances of microLEDs in the visible range.

Influence of surface recombination and the life time of minority carriers on the characteristics of MESFET (OPFET) GaN

The determination of the current voltage characteristics I–V of the optically controlled metal semiconductor field effect transistors (MESFET) termed as OPFET, in which we take into account, in channel region, of both photoconductive effect and photovoltaic effect at the Schottky gate, it is essential to understand its behaviors. Several analytical and empirical expressions have been proposed. In this paper, we present a analytical model of the OPFET GaN by the influence of surface recombination and the life time of minority carriers on the static properties of this component, given by the law A that taking into account the effects of the light on the component properties that take into account the effects of physical and geometrical parameters and conductance and transconductance.

Influence of Surface Recombination on Charge-Carrier Kinetics in Organic Bulk Heterojunction Solar Cells with Nickel Oxide Interlayers

Organic solar cells have many merits, including low cost and the ability to cover large and flexible substrates, yet there is much room to improve them. To maximize their efficiency, this study investigates the effects of surface recombination in a model system, in which the work function of electrode contacts is varied via oxygen-plasma treatment. The authors explain how changing the properties of the contact has a profound effect not only on device efficiency, but also on the interpretation of optoelectronic measurements of these devices.

Carrier Lifetimes and Influence of In-Grown Defects in N-B Co-Doped 6H-SiC

The thick N-B co-doped epilayers were grown by the fast sublimation growth method and the depth-resolved carrier lifetimes have been investigated by means of the free-carrier absorption (FCA) decay under perpendicular probe-pump measurement geometry. In some samples, we optically reveal in-grown carbon inclusions and polycrystalline defects of substantial concentration and show that these defects slow down excess carrier lifetime and prevent donor-acceptor pair photo luminescence (DAP PL). A pronounced electron lifetime reduction when injection level approaches the doping level was observed. It is caused by diffusion driven non-radiative recombination. However, the influence of surface recombination is small and insignificant at 300 K.

Influence of Surface Recombination on the Performance of SiNW Solar Cells and the Preparation of a Passivation Film

ABSTRACTAl2O3 was deposited on silicon nanowire (SiNW) arrays by atomic layer deposition (ALD) as a passivation layer to reduce surface recombination velocity. As a result, effective minority carrier lifetime was improved from 1.82 to 26.2 μs. From this result, the relative low-surface recombination rate of 2.73 cm/s was obtained from a calculation using one-dimensional device simulation (PC1D). The performance of SiNW solar cells was also simulated by considering the surface recombination velocity on the side of SiNWs using two-dimensional device simulation. It was found that Al2O3 deposited by ALD can improve open-circuit voltage of SiNW solar cells even if the structure has a high-aspect ratio and large surface area. Therefore, improvement in the performance of SiNW solar cells can be expected.

Influence of Surface Recombination on Forward Current–Voltage Characteristics of Mesa GaN $\hbox{p}^{+}\hbox{n}$ Diodes Formed on GaN Free-Standing Substrates

The influence of surface recombination on forward current-voltage (IF-VF) characteristics of gallium nitride (GaN) p+n diodes formed on GaN free-standing substrates was both experimentally and computationally investigated. In the temperature range of 373-273 K, the surface-recombination velocity 5 of 0.5-μm n GaN overetched circular-mesa diodes was derived, respectively, as 2-10 × 107 and 1 × 107 cm/s for diodes with and without a mesa-field-plate termination structure consisting of dielectric and metal layers. It was shown that IF (VF <; 2.9 V) is dominated by carrier recombination at the side surface of the etched n GaN. The IF-VF characteristics of the fabricated diodes were compared with the reported GaN p+n diodes with almost-zero overetched depth of n- GaN. The large IF of the latter diodes is attributed to enhanced photon recycling through photon reflection at the metal mirror. Moreover, reducing S to less than 105 cm/s is considered indispensible for achieving similar enhanced photon recycling in overetched terminated diodes.

Influence of surface recombination and interface states on the performance of β-FeSi2/c-Si heterojunction solar cells

To explore the origin of low conversion efficiency for novel β-FeSi2/c-Si heterojunction solar cells, the effect of surface recombination and interface states on the cell performance has been investigated by numerical simulation. The present results show that surface recombination of β-FeSi2 film plays an important role in limiting the cell property since the photovoltaic behavior of β-FeSi2 is quite sensitive to surface recombination due to its especial characteristic of very high optical absorption coefficient. Surface quality of β-FeSi2 film should be much improved for better cell performance. In addition, it is shown that interface states between β-FeSi2 film and crystalline silicon are critical to device characterization. Interface states should be minimized to obtain higher conversion efficiency. If surface recombination and interface states can be best suppressed, potential conversion efficiency for the cell may be up to 28.12% at 300K under illumination of AM 1.5, 100mW/cm2.

Evaluation of long carrier lifetimes in thick 4H silicon carbide epitaxial layers

The carrier lifetime of ∼265 μm thick n-type 4H silicon carbide epilayers prepared using the carbon-implantation/annealing method was evaluated. An extraordinarily long minority carrier lifetime of 18.5 μs and a high injection lifetime of 19.2 μs were evaluated from time-resolved photoluminescence and microwave photoconductivity decay measurements, respectively. Based on the relationship between the epilayer thickness and carrier lifetime, the influence of surface recombination on the carrier lifetime was eliminated, and the bulk lifetime and hole diffusion constant were discussed.

Current Gain Dependence on Emitter Width in 4H-SiC BJTs

This paper reports the fabrication of epitaxial 4H-SiC bipolar junction transistors (BJTs) with a maximum current gain β=64 and a breakdown voltage of 1100 V. The high β value is attributed to high material quality obtained after a continuous epitaxial growth of the base-emitter junction. The current gain of the BJTs increases with increasing emitter width indicating a significant influence of surface recombination. This “emitter-size” effect is in good agreement with device simulations including recombination in interface states at the etched termination of the baseemitter junction.

Influence of surface recombination on the burn-in effect in microwave GaInP/GaAs HBT's

In this paper, we report on the early increase of the dc current gain (burn-in effect) due to the electrical stress of carbon doped GaInP/GaAs heterojunction bipolar transistors (HBTs). Devices featuring different passivation layers, base doping, and emitter widths were investigated. The obtained data demonstrate that the burn-in effect is due to a reduction of the surface recombination located at the extrinsic base surface, around the emitter perimeter. It is concluded that the recombination centers are related to defects at the passivation/semiconductor interface and that, during the stress, they are passivated by hydrogen atoms released from C-H complexes.

Determination of the diffusion length from defect contrast by SEM-EBIC

Abstract The diffusion length (L) of minority carriers was determined from contrast of linear defects. Dislocation contrast was measured by EBIC at room temperature versus bias of a Schottky diode. It was shown for the first time that the slope of the contrast curves depends on L. The requirement to the SEM regime and EBIC geometry were formulated in a way to avoid influence of surface recombination on the measurements and diminish the role of other side effects as well.

Determination of minority-carrier lifetime and surface recombination velocity by optical-beam-induced-current measurements at different light wavelengths

An analysis of the optically generated excess current through a plane p-n junction perpendicular to the surface is given both for the steady state and for periodic generation. The finite dimensions of the sample are taken into account. The sample is assumed to be bounded by a plane parallel to the junction. An exponential light generation function according to Beer’s law is considered. By variation of the wavelength and thus the penetration depth of the light, the influence of surface recombination on the measured signal can be controlled. Therefore, the determination of bulk diffusion length and surface recombination velocity is unambiguously possible from a set of steady-state optical-beam-induced-current curves at different light wavelengths. From additional high-frequency measurements, the diffusion constant and thus the bulk lifetime of the excess carriers may be obtained. The results are demonstrated by measurements on various p+nn+diodes.

Influence of surface recombination on optically bistable semiconductor devices

The influence of carrier surface recombination on optical bistability of an electronic origin is predicted to lead to an optimum cavity length for low-power operation. The power (irradiance) levels for bistable switching are shown to be severely higher in the presence of strong surface effects. An optimization procedure for low-irradiance switching is described.

Surface recombination at semiconductor electrodes Part I. Transient and steady-state photocurrents

The influence of surface recombination on photocurrents at the illuminated semiconductor/electrolyte interface is considered. It is assumed that the surface states are located at a discrete energy in the band gap and that they communicate preferentially with the semiconductor. Expressions for the steady-state and transient photocurrent response are derived, and the effects of band-edge unpinning are discussed.

Surface recombination at semiconductor electrodes: Part I. Transient and steady-state photocurrents

The influence of surface recombination on photocurrents at the illuminated semiconductor/electrolyte interface is considered. It is assumed that the surface states are located at a discrete energy in the band gap and that they communicate preferentially with the semiconductor. Expressions for the steady-state and transient photocurrent response are derived, and the effects of band-edge unpinning are discussed.

The Influence of Surface Recombination and Trapping on the Cathodic Photocurrent at p‐Type III‐V Electrodes

The factors contributing to the large overpotential with respect to flatband potential required for hydrogen evolution and certain redox reactions at illuminated p‐type electrodes of various III–V compounds have been investigated. Results of photoelectrochemical studies, involving minority carrier transfer to redox systems in the electrolyte, indicate that surface states acting as recombination centers are important. Thin‐slice measurements with a p‐n junction show that the recombination velocity at the interface is indeed very high, even at potentials corresponding to a thick depletion region. Results of impedance measurements made with illuminated electrodes emphasize the importance of charge localization in surface states. A model based on surface recombination and electron trapping can explain the photocurrent‐potential and impedance characteristics of the p‐type electrodes.

The Influence of Surface Recombination on the Photoelectromagnetic (PEM) Effect in Semiconductors with Deep Traps

The Influence of Surface Recombination on the Photoelectromagnetic (PEM) Effect in Semiconductors with Deep Traps

The influence of the generation volume of minority carriers on EBIC

Analysis of electron-beam-induced current (EBIC) in the line scan method is described in the case of finite generation volume. The influence of surface recombination on EBIC is investigated, when the three-dimensional generation distribution is taken into account. When the accelerating voltage Va of an electron beam is low, the generation volume is assumed to be a point; surface recombination has a great effect on the shapes of curves of EBIC versus scanning distance and on the absolute value of EBIC. When Va becomes high, the generation volume can no longer be assumed to be a point; surface recombination does not affect the shape of EBIC versus scanning distance curves, but reduces the absolute value. The existence of a maximum value of EBIC near the barrier can be explained by an analysis using the finite generation volume. Accurate values of the physical parameters such as the diffusive length are estimated by fitting the experimental data to the theoretical curves for all accelerating voltages.

The influence of surface recombination on the double-injection negative-resistance

The influence of surface recombination on the double-injection negative-resistance

The influence of surface recombination on the double-injection switching

The influence of surface recombination on the double-injection switching