Electrical Transport in nGe-pGaAs Heterojunctions†
01 Jun 1966-International Journal of Electronics (Taylor & Francis Group)-Vol. 20, Iss: 6, pp 583-599
TL;DR: In this paper, a multi-step recombination-tunnelling model, similar to that used to describe the excess current in tunnel diodes, is developed to explain the observed electrical characteristics of nGe-pGaAs heterodes.
Abstract: A multi-step recombination-tunnelling model, similar to that used to describe the excess current in tunnel diodes, is developed to explain the observed electrical characteristics of nGe-pGaAs heterodiodes. Two different, but quite similar models are used to qualitatively describe the observed forward and reverse characteristics. Quantitative agreement with the experimental characteristics of the many devices presented is obtained by an empirical modification of the resulting equations. The lack of minority carrier injection in these devices is in agreement with the proposed model.
Citations
More filters
TL;DR: In this article, the authors present a systematic study on the electronic transport mechanisms of thin-film solar cells and propose two transport models, namely tunneling enhanced volume recombination (TV recombination) and tunable enhanced interface recombination, which allow to explain the observed features for all devices under consideration.
Abstract: This article presents a systematic study on the electronic transport mechanisms of CuGaSe2-based thin film solar cells. A variety of samples with different types of stoichiometry deviations, substrates and buffer layers is investigated. We propose two transport models, namely tunneling enhanced volume recombination and tunneling enhanced interface recombination, which allow to explain the observed features for all devices under consideration. The doping level of the absorber layer turns out to be the most decisive parameter for the electronic loss mechanism. The doping is influenced by the type of stoichiometry deviation as well as by the Na content of the substrate. High doping levels result in tunnel assisted recombination. The best solar cells display the lowest tunneling rates. For these devices treatments of the absorber surface by air-annealing and/or the deposition temperature of the CdS buffer layer are decisive for the final device performance. We use the investigation of the open-circuit voltage...
316 citations
TL;DR: In this paper, the forward current of all the junctions studied shows voltage and temperature dependence expressed as exp(−ΔEa f/kT) exp(AV), where ΔEa is the diffusion voltage and A is a constant.
Abstract: We have measured C‐V characteristics and temperature dependence of J‐V characteristics of undoped hydrogenated amorphous silicon (a‐Si:H) heterojunctions formed on p‐type crystalline silicon ( p c‐Si) substrates with different resistivities. It has been found that an abrupt heterojunction model is valid for a‐Si:H/p c‐Si heterojunctions, and the electron affinity of a‐Si:H has been estimated as 3.93±0.07 eV from C‐V characteristics. The forward current of all the junctions studied shows voltage and temperature dependence expressed as exp(−ΔEa f/kT) exp(AV), where ΔEa f and A are constants independent of voltage and temperature, being successfully explained by a multitunneling capture‐emission model. The reverse current is proportional to exp(−ΔEar/kT)(VD−V)1/2, where VD is the diffusion voltage and ΔEar is a constant. This current is probably limited by generation‐recombination process.
281 citations
TL;DR: In this paper, the authors studied the electrical characteristics and optical properties of GaN/InGaN multiple quantum well (MQW) light-emitting diodes (LEDs) grown by metalorganic chemical vapor deposition.
Abstract: We have studied the electrical characteristics and optical properties of GaN/InGaN multiple quantum well (MQW) light-emitting diodes (LEDs) grown by metalorganic chemical vapor deposition. It appears that there is an essential link between material quality and the mechanism of current transport through the wide-bandgap p-n junction. Tunneling behavior dominates throughout all injection regimes in a device with a high density of defects in the space-charge region, which act as deep-level carrier traps. However, in a high-quality LED diode, temperature-dependent diffusion-recombination current has been identified with an ideality factor of 1.6 at moderate biases. Light output has been found to follow a power law, i.e., L /spl prop/ I/sup m/ in both devices. In the high-quality LED, nonradiative recombination centers are saturated at current densities as low as 1.4 /spl times/ 10/sup -2/ A/cm/sup 2/. This low saturation level indicates that the defects in GaN, especially the high density of edge dislocations, are generally optically inactive.
224 citations
Cites background or methods from "Electrical Transport in nGe-pGaAs H..."
...At high reverse voltages, the data is in good agreement with band-to-band tunneling as predicated by Zener tunneling model [6]....
[...]
...Strong reverse tunneling behaviors have been also found in conventional III–V diodes [6], [7] and GaN p–n junctions [8]....
[...]
...The excess current could also result from a more complex process involving multiple-step tunneling-recombinations [6]....
[...]
TL;DR: In this paper, the leakage current of the SiO2 layer formed with 61 wt'% HNO3 at its boiling temperature of 113'°C has a 1.3 nm thickness with a considerably high density leakage current.
Abstract: Ultrathin silicon dioxide (SiO2) layers with excellent electrical characteristics can be formed using the nitric acid oxidation of Si (NAOS) method, i.e., by immersion of Si in nitric acid (HNO3) solutions. The SiO2 layer formed with 61 wt % HNO3 at its boiling temperature of 113 °C has a 1.3 nm thickness with a considerably high density leakage current. When the SiO2 layer is formed in 68 wt % HNO3 (i.e., azeotropic mixture with water), on the other hand, the leakage current density (e.g., 1.5 A/cm2 at the forward gate bias, VG, of 1 V) becomes as low as that of thermally grown SiO2 layers, in spite of the nearly identical SiO2 thickness of 1.4 nm. Due to the relatively low leakage current density of the NAOS oxide layer, capacitance–voltage (C–V) curves can be measured in spite of the ultrathin oxide thickness. However, a hump is present in the C–V curve, indicating the presence of high-density interface states. Fourier transformed infrared absorption measurements show that the atomic density of the SiO...
210 citations
TL;DR: In this paper, visible light emission from diodes made from poly(3-octylthiophene) was reported, and the authors used a soluble derivative of polythiophenes for fabrication.
Abstract: We report visible light emission from diodes made from poly(3‐octylthiophene). Use of a soluble derivative of polythiophene allows fabrication of the light emitting diodes by casting the polymer film from solution with no subsequent processing or heat treatment required. The devices emit dim red‐orange light with relatively low external quantum efficiencies, below 2.5×10−5 photons per electron at room temperature. Electrical characterization reveals diode behavior with rectification ratios greater than 102. The temperature dependence indicates that tunneling phenomena dominate the charge injection.
178 citations
References
More filters
01 Sep 1957
TL;DR: In this article, the authors show that the current due to generation and recombination of carriers from generation-recombination centers in the space charge region of a p-n junction accounts for the observed characteristics.
Abstract: For certain p-n junctions, it has been observed that the measured current-voltage characteristics deviate from the ideal case of the diffusion model. It is the purpose of this paper to show that the current due to generation and recombination of carriers from generation-recombination centers in the space charge region of a p-n junction accounts for the observed characteristics. This phenomenon dominates in semiconductors with large energy gap, low lifetimes, and low resistivity. This model not only accounts for the nonsaturable reverse current, but also predicts an apparent exp (qV/nkT) dependence of the forward current in a p-n junction. The relative importance of the diffusion current outside the space charge layer and the recombination current inside the space charge layer also explains the increase of the emitter efficiency of silicon transistors with emitter current. A correlation of the theory with experiment indicates that the energy level of the centers is a few kT from the intrinsic Fermi level.
1,934 citations
IBM1
TL;DR: In this article, the electrical characteristics of Ge-GaAs heterojunctions, made by depositing Ge epitaxially on GaAs substrates, are described and I-V and electro-optical characteristics are consistent with a model in which the conduction-and valence-band edges at the interface are discontinuous.
Abstract: The electrical characteristics of Ge-GaAs heterojunctions, made by depositing Ge epitaxially on GaAs substrates, are described. I–V and electro-optical characteristics are consistent with a model in which the conduction- and valence-band edges at the interface are discontinuous. The forbidden band in heavily doped (n-type) germanium appears to shift to lower energy values.
970 citations
TL;DR: In this article, the authors proposed a tunnelling-via-local-state model for the excess current in silicon junctions, which was shown to be applicable to excess currents in other materials.
Abstract: At low forward biases, a high current flows in Esaki junctions due to band-to-band tunnelling. At sufficiently high biases the current flows by normal forward injection. Between these two bias ranges, the current is unexpectedly high and has been called the excess current. A comprehensive experimental study has been made of this excess current in silicon junctions. It is shown that the properties of the excess current observed so far can be accounted for by a mechanism originally suggested by Yajima and Esaki, in which carriers tunnel by way of energy states within the forbidden gap. Based on this model, the following expression for the excess current, ${I}_{x}$, is proposed: ${I}_{x}\ensuremath{\sim}{D}_{x}\mathrm{exp}{\ensuremath{-}(\frac{{\ensuremath{\alpha}}_{x}{W}_{1}{e}^{\frac{1}{2}}}{2})[\ensuremath{\epsilon}\ensuremath{-}e{V}_{x}+0.6e({V}_{n}+{V}_{p})]},$ where ${D}_{x}$ is the density of states in the forbidden gap at an energy related to the forward bias, ${V}_{x}$, and the Fermi energies on the $n$ and $p$ sides are ${V}_{n}$ and ${V}_{p}$, respectively, $e$ is the electron charge, $\ensuremath{\epsilon}$ is the energy gap, ${W}_{1}$ is the junction width constant, and ${\ensuremath{\alpha}}_{x}$ is a constant containing a reduced effective mass, ${m}_{x}$. This formula describes the observed dependence of ${I}_{x}$ (i) on ${D}_{x}$, observed by introducing states associated with electron bombardment, (ii) on $\ensuremath{\epsilon}$, studied by the temperature variation of the diode characteristics, (iii) on ${V}_{x}$, verified from semilogarithmic plots of the forward characteristics, and (iv) on ${W}_{1}$, tested by using junctions of different widths. From these experiments, ${m}_{x}=0.3{m}_{0}$ to within a factor of 2.The origins of the states in the band gap are not known for certain though they are most likely the band edge tails inherent to heavily doped semiconductors. It is probable that the tunnelling-via-local-states model for the excess current in silicon is applicable to excess currents in other materials.
284 citations
144 citations