New porous silicon preparation technique has been suggested and realized with using vapor etching of silicon in iodine and HF contained vapors. It has been shown that vapor etching allows the preparation of luminescent porous layers on heavy doped (n<sup>++</sup> and p<sup>++</sup> type) silicon. Comparison of Raman and CW excitation PL measurements of vapor etched porous layer with typical anodized luminescent porous silicon indicated that they have in general similar structural and PL properties. Time resolved photoluminescence measurements reveal however that excitation recombination for iodine contained vapor etched samples is two times faster with higher photoluminescence efficiency, which can be interpreted as increasing of radiative recombination rate for luminescence centers in new nanocrystalline silicon.
Electroluminescent diodes fabricated on silicon substrates which emit at a wavelength of 1.5 micrometer have been demonstrated. The diodes operate at room temperature and exhibit good I-V characteristics. The diodes use an erbium tris(8-hydroxyquinoline) (ErQ) layer as electron transporting and emitting layer and use N, N'-diphenyl-N, N'-bis(3-methyl)-1,1'-biphenyl-4,4'-diamine (TPD) as the hole transporting layer. Hole injection into the diodes is from a p<SUP>++</SUP> silicon substrate anode and aluminum is used as the cathode electrode. The devices demonstrated start to exhibit electroluminescence at a voltage of approximately 17 V and the electroluminescence intensity rises sub-linearly with the current density through the device. At a drive voltage of 33 V the diodes have an internal efficiency of approximately 0.01%. We have measured the luminescence lifetime for the 1.5 micrometer emission and obtained a value of approximately 200 microsecond(s) . Using this value and estimating the total concentration of erbium present in the diodes we calculate a theoretical maximum optical power generation in these diodes of approximately 100 mW.
We have demonstrated that it is possible to product organic light emitting diodes containing lanthanide ions which provide sharp electroluminescence emission at a range of wavelengths in the near infrared including 0.9 micrometers , 0.98 micrometers , 1.064 micrometers , 1.3 micrometers and 1.5 micrometers . For devices grown on ITO substrates we have demonstrated bright electroluminescence at drive voltages of approximately 12 V. We have shown that these diodes can be integrated onto silicon substrates and use the silicon as the anode of the device. For erbium based devices which emit at a wavelength of 1.5 micrometers we have demonstrated devices with room temperature internal efficiencies of approximately 0.01% at a drive voltage of 33 V.
- The diffusion coefficient of interdiffusion in InGaAs/GaAs strained quantum wells has been determined as a function of time following implantation with gallium arsenic and krypton ions. All implants were shown to produce some collisional mixing. Gallium implantation produced no enhancement of the intermixing over unimplanted samples whilst krypton implantation produced a factor oftwo increase in the interdiffusion. Arsenic implantation produced a two step diffusion mechanism with a fast initialdiffusion(20 times unimplanted)and a steady state region similar to that observed with krypton implants. I.