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3 2004

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Photoreflectance and photoluminescence of thick GaN layers grown by HVPE

Kudrawiec R., Korbutowicz R., Paszkiewicz R., Syperek M., Misiewicz J.

Opto-Electronics Review

2004

Vol. 12, No. 4

435-439

Very thick (up to 100 µm) GaN layers grown by HVPE are investigated by photoreflectance (PR) and photoluminescence (PL) spectroscopies. The layers were deposited on a GaN buffer layer which was grown on a c-plane sapphire substrate by MOVPE. Both, N- and Ga-polar layers were selected to these investigations. We have observed a strong dependence of the optical properties on the polarity of GaN surface. We have obtained that the bandgap-related emission for Ga-polar layers is stronger and narrower than the emission for N-polar layers. Also, significant differences have been found in PR spectra of the two type layers. In the case of Ga-polar layer a broad PR resonance with Franz-Keldysh oscillation (FKO) related to the surface electric field (215 kV/cm) has been observed, while in the case of N-polar layer narrow resonances have been found as being predominant. No-FKO for N-polar layer indicates that the surface electric field for this layer is weak. It means that the surface barrier for N-polar GaN is much smaller than for Ga-polar GaN layer.

GaN grown in polar and non-polar directions

Liliental-Weber Z., Jasiński J., Zakharov D.

Opto-Electronics Review

2004

Vol. 12, No. 4

339-346

In this paper, defects formed in GaN grown by different methods are reviewed. Thin GaN films were grown on c-, m-, and a-planes on a number of substrates and typical defects as characterized by transmission electron microscopy are described. For polar epilayers grown on c-plane sapphire the typical defects are dislocations (edge, screw and mixed). The lowest dislocation density was obtained for homoepitaxial growth using molecular beam epitaxy (MBE) or hydride vapour phase epitaxy (HVPE). In these cases, the core structure of screw dislocations were studied in detail. In both cases, the cores are full. In the layers grown by HVPE the dislocations are decorated by pinholes stacked on top of each other. These pinholes are empty inside and their formation is attributed to impurities (oxygen) present in these layers. In these layers Ga-rich cores have been found. These were not observed in the layers grown by MBE on the top of the HVPE templates. Epilayers grown in non-polar directions (m- or a-plane) have a high density of planar defects (stacking faults) terminated by partial dislocations. Only low energy faults were found. The majority of these faults are formed at the interface with the substrate and propagate to the sample surface.

Advanced technology of AIII-BV and AIII-N structures for microelectronics application

Boratyński B., Korbutowicz B., Paszkiewicz B., Paszkiewicz R., Pucicki D., Radziewicz D., Ściana B., Tłaczała M.

Bulletin of the Polish Academy of Sciences. Technical Sciences

2004

Vol. 52, nr 4

291-299

In this work studies of MOVPE growth of InAlGaAs/ AlGaAs/GaAs heterostructures are presented. The HRXRD and SIMS measurements indicate the high structural and optical properties as well as high uniformity of thickness and composition of InAlGaAs quantum wells. This work is the first step towards elaboration of the technology of the strained InAlGaAs/GaAs heterostructures for advanced optoelectronic devices working in the visible part of the spectrum. The investigations of Si (n-type), Zn (p-type) b-doped GaAs epilayers and centre Si-b-doped InxGa1-xAs single quantum well (SQW) are presented. The b-doping layer was formed by SiH4 or DEZn introduction during the growth interruption. The electrical and optical properties of the obtained structures were examined using C-V measurement, EC-V electrochemical profiler, Raman spectroscopy (RS), photoreflectance (PR) and photocurrent (PC) spectroscopies. Technology of thick GaN layers grown on sapphire by HVPE is very promising as a part of freestanding GaN substrates manufacturing. Further works will be focused on the optimisation of growth, separating layers from substrates and surface polishing. The influence of the growth parameters on the properties of (Ga, Al)N/ Al2O3 and Mg dopant incorporation was studied.