Direct MBE growth of GaN on GaAs substrates for integrated short wavelength emitters

The growth and material properties of GaN heteroepitaxial layers on vicinal (1 0 0) and exact (1 1 1)B substrates have been investigated, using molecular beam epitaxy (MBE) with N₂ RF-plasma source. We examined the approach to grow GaN directly on the oxide desorbed GaAs, without the incidence of an As beam during oxide desorption or the following stages of growth. Perfect smooth surfaces were obtained on (1 1 1)B GaAs but excellent luminescence properties were observed on vicinal (1 0 0) GaAs. Four growth temperatures (T_G) were compared for the (1 0 0) orientation and a monotonic increase of photoluminescence intensity with increasing T_G, in the range of 570–680°C, was observed. The best surface morphology of less than 10 nm rms roughness was also determined, by atomic force microscopy, for the maximum (680°C) temperature. The layers exhibited up to 10¹⁷ cm⁻³ electron concentration and it could be compensated by Mg impurities. Metallizations of Pt and Pd gave ohmic contacts on GaN/GaAs (1 0 0) but a Schottky diode contact was achieved by Ir metallization. The obtained material properties are probably sufficient for realizing efficient GaN light emitters on (1 0 0) GaAs substrates.