Abstract: A photodetector circuit incorporates an APD detector structure (10) comprising a p? silicon handle wafer (12) on which a SiO2 insulation layer (14) is deposited in known manner. During manufacture a circular opening (16) is formed through the insulation layer (14) by conventional photolithography and etching, and an annular p+ substrate contact ring (18) is implanted in the handle wafer (12) after opening of the window (16). The APD itself is formed by implantation of a p region (20) and an n+ region (22). After the various implantation steps a metallisation layer is applied, and annular metal contacts are formed by the application of suitable photolithography and etching steps, these contacts comprising an annular contact (26) constituting the negative terminal and connected to the p+ substrate contact ring (18), an annular metal contact (28) constituting the positive terminal and connected to the n+ region (22) of the APD, and source and drain contacts (30) and (32) (not shown in FIG.

Abstract: A photodetector circuit incorporates an avalanche photodiode structure having a contact layer (14) forming an ohmic contact over an annular region (18) with the annular guard ring (8). In the fabrication process, the starting substrate can either be the handle wafer of a p? silicon-on-insulator wafer, or a p-Si substrate with an insulating SiO2 layer (4). A window (6) is produced in the insulating layer (4) by conventional photolithographic and etching. A n+ guard ring (8) is created by diffusing donor impurities into the substrate, and a thinner insulating SiO2 layer (22) is thermally grown so as to cover the exposed surface of the substrate within the window (6). P-type dopant is then implanted through the thin oxide layer to increase the doping level near the surface of the substrate. Subsequently a second window (24) is made in the insulating layer (22), and the layer (12) is then epitaxially grown selectively on the area of the substrate exposed by the window (24) in the insulating layer (22).

Abstract: A horizontal access semiconductor photo detector (2) comprises a horizontal light absorbing layer (8) for converting light into photo-current which layer is configured to confine light within it in whispering gallery modes of propagation. The detector is configured to have a first waveguide portion (18) and a second light confining portion (20, 21) arranged such that the waveguide portion couples light into the detector and transfers light into the light confining portion so as to excite whispering gallery modes of propagation around the light confining portion. The light absorbing layer may be part of the light confining portion or alternatively light can be coupled into the light confining portion or alternatively light can be coupled into the light absorbing layer from the light confining portion by evanescent coupling. The excitation of whispering gallery modes within the light absorbing layer significantly increases the effective absorption coefficient of the light absorbing layer.

Abstract: A horizontal access semiconductor photo detector (2) comprises a horizontal light absorbing layer (8) for converting light into photo-current which layer is configured to confine light within it in whispering gallery modes of propagation. The detector is configured to have a first waveguide portion (18) and a second light confining portion (20, 21) arranged such that the waveguide portion couples light into the detector and transfers light into the light confining portion so as to excite whispering gallery modes of propagation around the light confining portion. The light absorbing layer may be part of the light confining portion or alternatively light can be coupled into the light confining portion or alternatively light can be coupled into the light absorbing layer from the light confining portion by evanescent coupling. The excitation of whispering gallery modes within the light absorbing layer significantly increases the effective absorption coefficient of the light absorbing layer.

Abstract: A method of making semiconductor quantum wires, and a light emitting device employing such wires, employs a semiconductor wafer as starting material. The wafer is weakly doped p type with a shallow heavily doped p layer therein for current flow uniformity purposes. The wafer is anodized in 20% aqueous hydrofluoric acid to produce a layer 5 microns thick with 70% porosity and good crystallinity. The layer is subsequently etched in concentrated hydrofluoric acid, which provides a slow etch rate. The etch increases porosity to a level in the region of 80% or above. At such a level, pores overlap and isolated quantum wires are expected to form with diameters less than or equal to 3 nm. When excited, the etched layer exhibits photoluminescence emission at photon energies well above the silicon bandgap (1.1 eV) and extending into the red region (1.6-2.0 eV) of the visible spectrum.

Abstract: An electroluminescent silicon device (10) includes a silicon structure (12) which comprises a bulk silicon layer (14) and a porous silicon layer (16). The porous layer (16) has merged pores (20) which define silicon quantum wires (18). The quantum wires (18) have a surface passivation layer (22). The porous layer (16) exhibits photoluminescence under ultra-violet irradiation. The porous layer (16) is pervaded by a conductive material such as an electrolyte (24) or a metal (48). The conductive material (24) ensures that an electrically continuous current path extends through the porous layer (16); it does not degrade the quantum wire surface passivation (22) sufficiently to render the quantum wires (18) non-luminescent, and it injects minority carriers into the quantum wires. An electrode (26) contacts the conductive material (24) and the bulk silicon layer has an Ohmic contact (28). When biased the electrode (26) is the anode and the silicon structure (12) is the cathode.

Abstract: A method of making semiconductor quantum wires employs a semiconductor wafer (14) as starting material. The wafer (14) is weakly doped p type with a shallow heavily doped p layer therein for current flow uniformity purposes. The wafer (14) is anodised in 20% aqueous hydrofluoric acid to produce a layer (5) microns thick with 70% porosity and good crystallinity. The layer is subsequently etched in concentrated hydrofluoric acid, which provides a slow etch rate. The etch increase porosity to a level in the region of 80% or above. At such a level, pores overlap and isolated quantum wires are expected to from with diameter less than or equal to 3 nm. The etched layer exhibits photoluminescence emission at photon energies well above the silicon bandgap (1.1 eV) and extending into the red region (1.6-2.0 eV) of the visible spectrum.

Abstract: A method of making semiconductor quantum wires employs a semiconductor wafer as starting material. The wafer is weakly doped p type with a shallow heavily doped p layer therein for current flow uniformity purposes. The wafer is anodised in 20% aqueous hydrofluoric acid to produce a layer microns thick with 70% porosity and good crystallinity. The layer is subsequently etched in concentrated hydrofluoric acid, which provides a slow etch rate. The etch increases porosity to a level in the region of 80% or above. At such a level, pores overlap and isolated quantum wires are expected to form with diameters less than or equal to 3 nm. The etched layer exhibits photoluminescence emission at photon energies well above the silicon bandgap (1.1 eV) and extending into the red region (1.6-2.0 eV) of the visible spectrum.

Abstract: A direct current electroluminescent device having a phosphor layer and coating electrodes, at least one of which is translucent, which has interposed between the phosphor layer and at least one of said electrodes a thin non-planar layer of an electrically non-conducting substance. The non-planar layer may have a cross section of undulating outline or may be a discontinuous layer, e.g. in the form of closely spaced dots. Preferably the non-planar layer is translucent and is arranged between the phosphor layer and a translucent electrode. Suitable materials for the non-planar layer include silicon monoxide, silicon dioxide, germanium dioxide, magnesium fluoride, cadmium fluoride, yttrium fluoride, yttrium oxide, zinc sulphide, copper sulphide.