SOME ASPECTS OF GAN GROWTH ON GAAS(100) SUBSTRATES USING MOLECULAR-BEAM EPITAXY WITH AN RF ACTIVATED NITROGEN-PLASMA SOURCE

We have investigated hew supplying active nitrogen from an RF activated plasma source under various plasma conditions influences certain aspects of the growth of GaN films on GaAs(100) substrates, using molecular beam epitaxy. In the first instance, the quantity of active nitrogen generated by the source was found to have a strong dependence on both the RF power and amount of nitrogen gas supplied to the plasma. In addition, the degree of optical discharge from the plasma was observed to give a semi-quantitative measure of active nitrogen. No observable loss of nitrogen from the sample surface in the temperature range 450 to 680 degrees C was found during GaN growth. Scanning electron microscopy on the cleaved edges of the GaN/GaAs(100) samples showed the GaN layer to be polycrystalline with a columnar nature typical of a highly lattice mismatched material system. X-ray diffraction measurements indicated that the GaN layers were entirely wurtzite in structure, with the full width at half maximum of the GaN (0002) reflection in the range 9 to 11.5 arcmin. A broad peak centred at around 3.4 eV was recorded using room temperature photoluminescence measurements on the layers.