LP-MOCVD GROWN (INAS)(M)(GAAS)(M) SHORT-PERIOD SUPERLATTICES ON INP

(InAs)(m)(GaAs)(m) (1 less than or equal to m less than or equal to 12 ) short period superlattices (SPSs) have been grown on semi-insulated InP substrates with a 200 nm InP cap layer using low pressure metalorg anic chemical vapor deposition (MOCVD). According to double crystal x- ray diffraction and transmission electron microscopy results, the crit ical layer thickness of(InAs),(GaAs), SPS was observed to be similar t o 30 Angstrom (m = 5). For the SPS below the critical layer thickness, mirror-like surface morphology was found without defects, and strong intensity Fourier transformed photoluminescence (FT-PL) spectra were a lso obtained at room temperature. The SPS with m = 4 showed a drastic improvement in photoluminescence intensity of order of two compared to an InGaAs ternary layer. However, the SPS with a large value of m (m greater than or equal to 6), rough surface was observed with defects, with broad and weak FT-PL spectra. The surface morphology of SPS was g reatly affected by the substrate orientation. The SPS with m = 5 was g rown on two degree tilted substrate from (100) direction and showed po or surface morphology as compared to the one grown on (100) exact subs trate Moreover, the SPS grown on a (111)B substrate showed a rough tri angular pattern with Nomarski optical microscopy. In-situ thermal anne aled SPS with m = 4 showed a 18 meV increase in PL peak energy compare d to the as-grown sample due to phase separation resulting from therma l interdiffusion.