A confined random-particle flux (such as photons in an electroluminescent diode, integrating sphere, or room, music or other phonons in an auditorium. gas molecules in an imperfect vacuum chamber, neutrons in a reactor, etc.) is analyzed, and simple expressions are shown to exist for the mean path length. transit time, surface transmissivity, projected area, absorption rate, etc.. that arise in its description. The results are applied to a theoretical and experimental analysis of the coupling of photons from their source within an indirect-band-gap electroluminescent diode (or within a sufficiently transparent heterostructure direct-band-gap diode) into the ambient or into a multimode optical fiber. We find that about two-thirds of the internally generated photons will reach air from an encapsulated rough-sawed red-emitting GaP(Zn,O) electroluminescent diode of reasonably high purity and contact reflectivity, whereas in a comparable green-emitting GaP(N) diode only about one-fourth of the photons escape while three-fourths are absorbed within the diode bulk and at its contacts.[This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP:

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A NEW ELECTRODE STRUCTURE for charge-coupled devices which overcomes problems associated with the original singlelevel metal approach will be described. Each set of transfer electrodes of a three-phase CCD is formed in a separate level of polycrystalline silicon; Figure 1. The structure is fabricated in the following manner. A first level of polysilicon is deposited onto an oxidized silicon wafer, then doped with phosphorus and steam oxidized. Using this oxide as an etch mask for the polysilicon the first set of electrodes is defined. Part of the remaining masking oxide and the exposed gate oxide are now removed to obtain equal gate oxide thicknesses under all electrode levels. Subsequently a new gate oxide is thermally grown and the electrodes are partly oxidized. This thermallygrown oxide provides an insulator of high integrity between electrode levels. These processes are repeated t o form the second and third levels of polysilicon. A final phosphorous gettering step is introduced before the contact windows t o all polysilicon levels and to the substrate are etched. A fourth level of true metal(normal1y Ti-Pd-Au) is then applied to provide high conductivity bus bars, bonding pads and, if desired, a light shield in some areas. This level generally contains only large features that are restricted to the periphery of the device. An exception is the defining slit in a linear image sensor.This process results in a completely sealed structure with overlapping electrodes; Figure 2. Problems associated with the bare transfer gaps in single-level metal structures, such as instabilities and sensitivity to the ambient, are thus eliminated. Good control over the interface potential and the strong fringe fields of a three-phase structure result in exceptionally good transfer efficiencies.The new structure also considerably relaxes the demands on mask making and photolithography. No narrow gaps have to be etched. The smallest features are the electrodes themselves and most gaps are larger.Furthermore intralevel shorts no longer cause fatal defects since only electrodes connected by the same bus bars are shorted together. In many places such a short causes no harm at all. Only if such a bridge of excess metal occurs above a transfer channel, within the first or second electrode level, mixing of subsequent charge packets occurs, giving rise to charge smearing in that channel. Fatal defects are caused by interlevel shorts in the areas of electrode overlap. However, the pinhole density in a thermally-grown oxide on polysilicon can -' Picturephone@ be extremely low. These two factors taken together thus promise high fabrication yields.Conversely the simple cell geometry, the relaxed tolerances and a relatively uncritical mask alignment allow the fabrication of very small cells. The cell length can be on the order of 3 W, where W represents the minimal allowable feature dimension.In fabricating cells of minimum size the electrodes in the third level can be formed as a continuous layer of polysilicon. The small cell size makes ...

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