Showing papers by "Leigh T. Canham published in 1992"
TL;DR: In this article, an analytical expression for the exciton energy gap at 4.2 K valid for x < 0.24 was derived from the no-phonon line energies: ESX(x) = 1.155−0.874x+0.376x2 eV.
Abstract: The systematic study of band‐edge luminescence in pseudomorphic Si/Si1−xGex/Si double‐heterostructure layers is reported for a wide composition range, 0.12
191 citations
TL;DR: In this article, a visible electroluminescence (EL) was obtained from porous silicon cathodically biased in an aqueous electrolyte containing either persulphate or peroxide ion.
Abstract: Visible electroluminescence (EL) has been obtained from porous silicon cathodically biased in an aqueous electrolyte containing either the persulphate or the peroxide ion. EL efficiencies of up to 0.1% have been obtained from porous silicon formed on both n‐type and p‐type substrates for the application of only a few volts bias. In subdued lighting, the EL is easily visible to the naked eye at excitation densities of 0.1 W cm−2. EL is obtained only from porous silicon capable of giving photoluminescence (PL); the EL and PL spectra are broadly similar in width and peak wavelength. The EL spectra are reversibly shifted to shorter wavelengths as the magnitude of the bias is increased. In contrast with the previously reported EL under anodic conditions, this cathodic EL process does not irreversibly oxidize the porous silicon skeleton.
150 citations
TL;DR: The concept of integrated circuits (ICs), conceived in the 1950s, overcame what had been called a "tyranny of numbers" problem as discussed by the authors, that of connecting and soldering together prohibitive numbers of small, discrete electronic components.
Abstract: Silicon is the second most abundant element in the Earth's crust. As well as being cheap, it possesses certain physical and chemical properties that have made it the dominant material in microelectronics for over three decades. The concept of integrated circuits (ICs), conceived in the 1950s, overcame what had been called a "tyranny of numbers" problem – that of connecting and soldering together prohibitive numbers of small, discrete electronic components. But it was the 1960s, when the practical fabrication of such devices became possible, that heralded the silicon chip revolution.
35 citations
TL;DR: In this paper, resonantly excited photoluminescence (PL) spectroscopy of highly porous silicon is reported, where the authors observe satellite structure due to the participation of momentum-conserving phonons in the optical transitions.
Abstract: We report resonantly excited photoluminescence (PL) spectroscopy of highly porous silicon. In the PL spectra we observe satellite structure due to the participation of momentum-conserving phonons in the optical transitions. The momentum-conserving role of these phonons, together with their energies and relative coupling strengths, demonstrate beyond doubt that crystalline silicon, which has already been shown to be the dominant constituent of unoxidised porous silicon, also forms the luminescent material. We show that the theory of quantum confinement in crystalline silicon wires can explain our results and those of other experiments, if the electron-hole interaction, and the localisation of carriers by fluctuations in wire width, are taken into account.
15 citations
TL;DR: In this article, the structure of the oxidised porous Si was examined by transmission electron microscopy, while its oxygen content was determined by X-ray microanalysis, showing that crystalline Si nanostructures remain in the oxidized porous material and account for its luminescence properties.
Abstract: Luminescent oxidised porous Si is produced by rapid thermal annealing of the anodised material in a dry oxygen ambient. Its light-emitting properties are studied by both photoluminescence and cathodoluminescence methods. The structure of the oxidised material is examined by transmission electron microscopy, while its oxygen content is determined by X-ray microanalysis. These investigations show that crystalline Si nanostructures remain in the oxidised porous material and account for its luminescence properties. The work demonstrates that the speculated importance of either Si-based amorphous phases or the interesting material, siloxene, in this regard is unrealistic.
12 citations
TL;DR: In this article, the depth dependence of the photoluminescence (PL) spectrum, both in terms of intensity and wavelength of the peak, is correlated with the electrochemical and chemical processes occurring during the formation of the porous silicon.
Abstract: The depth dependence of the photoluminescence (PL) spectrum, both in terms of intensity and wavelength of the peak, is correlated with the electrochemical and chemical processes occurring during the formation of the porous silicon. The depth dependence of the intensity of the electroluminescence (EL) under both anodic bias and cathodic bias, in solutions containing 1M H 2 SO 4 and 0.1M Na 2 S 2 O 8 , is found to be identical with that of the PL. These observations strongly suggest that the silicon skeleton is highly conductive during electrolytic EL, in marked contrast to its high resistivity in air. Strong evidence is provided linking the electrolytic EL to the PL. We extend the quantum confinement based model for PL to the case of electrolytic EL.
6 citations