Complete Report - University of New South Wales

Additional experimental diffi culties were encountered in the attempt to increase the depth
of the holes to about 1µm, which is the thickness of the thickest and currently most effi cient
SOI LEDs. Different attempts are currently being made to achieve structures with a higher
aspect ration. In this context a number of different RIE recipes have been investigated and
alternatively the possibility to use a chromium mask in order to transfer the EBL pattern
into to the silicon layer has been investigated with some success. First photoluminescence
studies on SOI layers textured with photonic crystals are planned for the near future.
A further interesting aspect of the photonic crystal work within the SOI group is the recent
observation by S.G. Cloutier et al. [S.G. Cloutier et al.,Nature Materials 4, 887 (2005)] that
optical gain associated with a so called A-centre could be observed at a wavelength of
1278nm at lower temperatures from silicon on insulator samples patterned with photonic
crystal structures. Given the signifi cance that a successful demonstration of optical gain in
an electrically pumped silicon device would have, we will carefully investigate whether this
emission is also observed from photonic crystal structured SOI LEDs.
Fig. 4.6.4.4: Negative impact of the proximity
effect on larger area photonic crystal
structures.
Fig. 4.6.4.5: Improved periodicity
and reduced proximity effects due to
reducing the acceleration voltage during
the EBL patterning of the PMMA.
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