Visible light emission from heavily doped porous silicon homojunction <i>pn</i> diodes

Chen, Zhiliang; Bosman, G.; Ochoa, Romulo

doi:10.1063/1.109603

Cited by 70 publications

(15 citation statements)

References 12 publications

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“…Recently, EL devices have been studied with various approaches. These approaches include simple metal/porous silicon junctions [4±6], hole injection at porous silicon/liquid interface [7±9], p±n porous silicon junctions [10] and conducting polymer [11] or ITO covered porous silicon structures.…”

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confidence: 99%

Optoelectronic Characterisation of Porous Silicon/CdS and ZnS Systems

Gokarna

Bhoraskar

Pavaskar

et al. 2000

phys. stat. sol. (a)

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Ultra thin films of CdS and ZnS were deposited on porous silicon by using the liquid±liquid interface reaction technique (LLIRT) which was similar to the Langmuir Blodgett method. The photoluminescence (PL) intensity after deposition of CdS and ZnS was observed to increase by more than two factors and was associated with a blue shift. Junction I±V characteristics were studied for various thicknesses of the deposited films. The rectifiying behaviour of I±V characteristics indicates the formation of junctions with porous silicon. Hall measurements were used to estimate the extrinsic properties of the overlayers as well as those of porous silicon. The change in the I±V characteristics after annealing of the deposited samples is also reported.Introduction Porous silicon which is obtained by electrochemical etching of silicon in diluted HF, at different current densities, is acquiring the status of a very important and versatile optoelectronic material. Of critical relevance to device implementation with this material are recent accounts stating efficient electroluminescence (EL) in porous silicon [1±3]. Formation of stable rectifying junctions with porous silicon, with good forward and reverse characteristics, is one of the most challenging problems for the proper exploitation of this material in the device industry. Recently, EL devices have been studied with various approaches. These approaches include simple metal/porous silicon junctions [4±6], hole injection at porous silicon/liquid interface [7±9], p±n porous silicon junctions [10] and conducting polymer [11] or ITO covered porous silicon structures.Present paper explores the possibility of using wide band gap II±VI semiconducting compounds, like CdS and ZnS, in conjunction with porous silicon for fabrication of electroluminescent devices. Ultrathin films of CdS and ZnS were chemically prepared by the liquid±liquid interface reaction technique (LLIRT) [12] and deposited onto the p-type porous silicon substrates. PL spectroscopy was extensively used for studying the light emission before and after the deposition. Formation of rectifying junctions in both these cases have been studied using I±V characteristics. Room temperature Hall measurements have been used for identifying the extrinsic activity of the surface of the semiconductor. This method provides an easy access of formation of heterojunctions at low temperatures.

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Optoelectronic Characterisation of Porous Silicon/CdS and ZnS Systems

Gokarna

Bhoraskar

Pavaskar

et al. 2000

phys. stat. sol. (a)

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“…Kocka, 1994); (psi) has many unique characteristics such as direct and wide modulated energy band gap , high resistivity , vast surface area-to-volume ratio and the same single-crystal structure as bulk silicon .Those advantages make it a suitable material for photodetectors (Nobuyoshi Koshida and Hideki Koyama. 1992) (Zhiliang Chen, Gijs Bosman and Romulo Ochoa. 1993).…”

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Design and Fabrication of Nanostructures Silicon Photodiode

Alwan¹,

Jabbar²

2011

MAS

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A highly sensitive (metal/nanostructure silicon /metal) photodiode has been fabricated from rapid thermal oxidation (RTO) and rapid thermal annealing (RTA) processes, of nanostructure porous silicon prepared by laser assisted etching.Photoresponse was investigated in the wavelength range (400-850nm). A responsivity of (3A/W) was measured at (450 nm) with low value of dark current of about (1 µA /cm 2 ) at 5 volt reverse bias.

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“…These devices were reported to have very low quantum efficiencies (Ͻ10 Ϫ6 ) and require high operating voltages. More recently, different designs 4,5 and better contact materials [6][7][8] have led to some improvement in the electrical and luminescent properties. The reasons for the low EL efficiency are not understood, but it has been suggested that the ease with which carriers are injected into luminescent states and the transport mechanisms in the porous silicon play an important role.…”

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Electroluminescence from porous silicon due to electron injection from solution

Kooij

Despo

Kelly

1995

Applied Physics Letters

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We report on the electroluminescence from p-type porous silicon due to minority carrier injection from an electrolyte solution. The MV ϩ• radical cation formed in the reduction of divalent methylviologen is able to inject electrons into the conduction band of crystalline and porous silicon. The electrochemistry of this redox process at silicon electrodes is briefly described, and electroluminescence due to recombination of the injected electrons with holes from the substrate is described. The results are discussed in terms of a semiconductor model. © 1995 American Institute of Physics.One of the main reasons for the extensive research on porous silicon is the prospect of integrating optical functions into all-silicon devices. To make a device capable of showing electroluminescence ͑EL͒, electrons and holes have to be injected into the porous silicon structure. Radiative recombination of these carriers will give rise to light emission. The first luminescent solid state devices based on this material 1-3 consisted of a porous layer on a crystalline substrate. A semitransparent Au or transparent conducting oxide electrode was deposited on top of the porous layer. These devices were reported to have very low quantum efficiencies (Ͻ10 Ϫ6 ) and require high operating voltages. More recently, different designs 4,5 and better contact materials 6-8 have led to some improvement in the electrical and luminescent properties. The reasons for the low EL efficiency are not understood, but it has been suggested that the ease with which carriers are injected into luminescent states and the transport mechanisms in the porous silicon play an important role. 9Much higher efficiencies were obtained using a liquid electrolyte junction which contacts the whole porous structure. [10][11][12] The mechanism of the strong visible emission from n-type porous silicon is thought to be similar to that for conventional semiconductors. Electron capture from the valence band, i.e., hole injection, is achieved by a strong oxidizing agent ͑electron acceptor͒ in the solution. At appropriate bias the injected holes recombine with electrons from the conduction band. If this recombination is radiative, EL characteristic of the semiconductor can be observed. 13A similar mechanism should hold for p-type semiconductors, only now electron injection into the conduction band is required. This is possible if the occupied energy levels of the redox couple in the solution overlap with the conduction band of the semiconductor. Thus, a strong reducing agent ͑electron donor͒ has to be used. To our knowledge there have been no reports of EL from p-type porous silicon due to minority carrier injection by a reducing agent in solution.14 Light emission during anodic oxidation of p-type porous silicon in indifferent electrolyte has been reported. 15 This has been attributed to electrons released during oxidation of Si-H surface species or of Si-Si bonds. However, this explanation may be suspect as luminescence is also observed under similar conditions at n-type porous...

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Visible light emission from heavily doped porous silicon homojunction pn diodes

Cited by 70 publications

References 12 publications

Optoelectronic Characterisation of Porous Silicon/CdS and ZnS Systems

Optoelectronic Characterisation of Porous Silicon/CdS and ZnS Systems

Design and Fabrication of Nanostructures Silicon Photodiode

Electroluminescence from porous silicon due to electron injection from solution

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