Complete Report - University of New South Wales

The theory of hot carrier absorbers has been extended to include a greater understanding of
phononic transport and a recognition of similarities to the required properties of thermoelectric
materials (see “Hot Carrier Absorbers” in Section 5.5 in 2003 Annual Report). In particular
the specifi c mechanisms which can slow cooling by enhancing the “phonon bottleneck effect”
in QW and QD superlattices are being identifi ed. Experimental evidence of such reduced
cooling in QW superlattices has been identifi ed in the literature. (See section “Hot Carrier
Absorbers” in section 4.5 in 2004 Annual Report). This work has been extended further in
2005 with modelling of the specifi c phonon mechanisms and quantum dot conditions that
can give an enhanced ‘phonon bottleneck effect’ in QD nanostructured materials.
A.12
Demonstration of the quantum confined Stark effect in silicon as the basis of a highspeed
silicon modulator).
Devices of an appropriate structure were fabricated during 2003, but silicon layers needed
to be thinner to demonstrate this effect. Progress was made in 2004 and 2005 in reducing
the thickness of these layers, that are now close to the desired value.
A.13
Evaluation of the optical constants of quantum confined silicon SOI devices as a
function of layer thickness.
Relevant data have been reported in section 5.5 of the 2003 Annual Report and section 4.6
of the 2004 report. Photoluminescence properties have been characterised. Conversion
to optical constants requires accurate knowledge of the dimensions of the confi ned material.
Measurement of these produces some experimental challenges, presently being addressed.
The most accurate method seems to be by identifying photoluminescence features
corresponding to regions differing by the presence of one additional atomic plane in the
region under test. However, fi nding an independent technique that is able to confi rm this
interpretation of the data has provided a challenge.
Other work quantifying the evidence for QDs and their dimensions is continuing. This includes
analysis of HRTEM, high resolution SIMS and synchrotron XRD.
A.14
Improvement of light emission efficiency of silicon diodes above levels already
demonstrated, to maintain Australian leadership and as a test bed for integrated
devices.
Australia retains leadership in the bulk silicon luminescence fi eld, although efforts during the
last 12 months have concentrated on integrated devices.
A.15
Demonstration of high light emission efficiency in silicon LEDs integrated into
microelectronic chips.
Effi ciencies of 2x10 -6 have been demonstrated, although further improvements are expected
as devices become thinner.
A.16
Demonstration of high speed modulation of output of silicon light emitting diodes.
Modulation has been demonstrated, but not yet at high speed.
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