SMA - Annual Report 20045/2005


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Project abstracts can be viewed from the CD-ROM which is enclosed or the SMA website (http://www.sma.nus.edu.sg).

AMM&NS Programme	HPCES Programme	IMST Programme	MEBCS Programme
CS Programme

IMST Programme

DR LOKE WAN KHAI Expertise: Growth of compound semiconductor (III-V and III-N-As) using solid source molecular beam epitaxy (MBE). Optical, electrical and structural characterization of semiconductor materials which involves measurements using techniques such as low-temperature photoluminescence, x-ray diffraction, atomic force microscopy, scanning electron microscopy and Hall effects

Nitride-Arsenide Compound Semiconductor (GaInNAs and GaNAs)

Project Advisor (Singapore)	:	Prof Yoon Soon Fatt

Duration	:	January 2004 to August 2004

Project Abstract:

Radio-frequency (rf) plasma assisted molecular beam epitaxial growth of GaNAs and GaInNAs has been investigated in previous work, with suitable growth parameters being developed. In particular, the post-growth rapid thermal annealing (RTA) effect on the GaNAs films grown on GaAs (100)-oriented substrate was investigated. The GaNAs films exhibit an overall blueshift in energy and an intermediate redshift of in the low-temperature (4K) photoluminescence (PL) spectra when subjected to different annealing temperature. This result suggests a possible mechanism where the GaNAs layer may have undergone an intermediate substitutional-interstitial diffusion. Samples annealed at 700-750oC showed 1.7-2.1 times improvement in integrated PL intensity and 1.6-1.8 times reduction in PL full width half maximum (FWHM) as compared to the as-grown sample. The change in diffused scattering intensity and crystal truncation rod in x-ray reciprocal space mapping (RSM) of the GaNAs samples subjected to different annealing temperature was also investigated. The effect of nitrogen and indium incorporation on the structural and optical properties of GaInNAs with low lattice mismatch to GaAs grown by the rf nitrogen plasma assisted method has also been investigated. The results show that excessive introduction of nitrogen during the growth of GaInNAs may lead to greater incorporation of interstitial nitrogen and degradation in crystal quality. This effect is more significant in GaInNAs compared to GaNAs. By changing the In composition and fixing the N incorporation rate, a sample of Ga_0.924 In_0.076 N_0.026 As_0.974/GaAs with relatively low lattice mismatch of -896ppm (or ~8.96x10-4) was successfully grown. Low-temperature (4K) PL emission at 1518nm (long wavelength) for this sample was observed.

Optoelectronic Integration/Optical Interconnects

Project Advisor (Singapore)	:	Prof Yoon Soon Fatt

Project Advisor (MIT)		Prof Clifton G. Fonstad Jr.

Duration	:	January 2004 to August 2004

Project Abstract:

An optoelectronic integration project in collaboration with MIT is to develop and apply RM3 (recess mounting with monolithic metallization) technologies, a technique pioneered by Professor Clifton G. Fonstad Jr. and his research team, for heterogeneous integration. One important part of this project undertaken by NTU is to epitaxially grow the InP-based heterostructures. This is followed by integration process using APB (aligned pillar bonding) or MASA (magnetically assisted statistical assembly) technologies in MIT. Such technologies will be of great use in producing optoelectronic integrated circuits (OEICs) for optical clock distribution, diffuse optical tomography, and smart pixel arrays. Other potential new applications of these technologies in intra- and interchip optical signal interconnects, in fluorescent dye detection and imaging for biomedical applications, and in III-V mini-IC integration on Si-CMOS for enhancing off-chip drive capabilities are outlined.

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