We report the structural, electrical and optical properties of bulk InAsN alloy with various nitrogen contents deposited on (100) InP substrates using plasma-assisted gas-source molecular beam epitaxy. From absorption measurements, it is found that the fundamental absorption energy of InAsN is higher than that of InAs due to the Burstein-Moss effect resulting from the high residual carrier concentration in InAsN. To deduce the 'real' band-gap energy of InAsN samples, the energy shift due to the Burstein-Moss effect and the band-gap narrowing effect are calculated by using a self-consistent approach based on the band-anticrossing (BAC) model [Shan et al.: Phys. Rev. Lett. 82 (1999) 1221. After correction, the 'real' band-gap energy of InAsN samples decreases as N increases. The electron effective mass of InAsN is also investigated by plasma-edge measurement. We found a sizeable increase of the electron effective mass in these InAsN alloys, which is consistent with the theoretical predictions based on the BAC model.

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We report the investigation on the growth conditions and optical properties of cubic GaN films grown on (001) GaAs substrate by using RF plasma assisted gas source MBE. The cubic GaN films were deposited at different Ga to N flux ratios that were determined by deposition rates directly. Three growth regimes, namely, Ga droplet, intermediate Ga stable, and N stable regime, are defined in the growth diagram. Optical quality of these films was determined by using photoluminescence (PL). Micro-Raman scattering were performed to analyze the crystallinity of the films. Optimal growth condition of cubic GaN is on the boundary of intermediate Ga stable regime and Ga droplet regime at a growth temperature of Ts = 720°C.