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 activate d plasma source under various plasma conditions influences certain asp ects of the growth of GaN films on GaAs(100) substrates, using molecul ar beam epitaxy. In the first instance, the quantity of active nitroge n generated by the source was found to have a strong dependence on bot h the RF power and amount of nitrogen gas supplied to the plasma. In a ddition, 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 micros copy 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 in dicated that the GaN layers were entirely wurtzite in structure, with the full width at half maximum of the GaN (0002) reflection in the ran ge 9 to 11.5 arcmin. A broad peak centred at around 3.4 eV was recorde d using room temperature photoluminescence measurements on the layers.