Transmission electron diffraction (TED) was used to observe extra diffraction spots in the TED patterns of molecular beam epitaxial GaAs1−y Sby layers with y=0.25, 0.50, and 0.71 grown at 520 °C on (001) GaAs substrates. Half-order diffraction spots in the TED patterns indicated ordering on the (1̄11) and (11̄1) planes of the Group V sublattice, and streaks with subsidiary spots indicated a modulation in the [110] direction with a periodicity of ∼4d110 . Streaks in the [001] direction indicated monolayer disruptions of the {111} ordering and the [110] modulation in the [001] direction. As the composition parameter y varied, there were progressive changes in the {111} ordering, the [110] modulation, and the [001] disruptions, and these correlated with corresponding changes in the reconstruction of the dangling bonds at the growing layer surface, as determined by reflection high-energy electron diffraction. A model is proposed to explain the observed effects in terms of ordered atomic arrangements of the Group V atoms resulting from the surface reconstruction being incorporated into the bulk epitaxial layers.
1.3 pm GalnAsP/lnP GRIN SCH MQW laser diodes grown by low-pressure MOCVD were operated without mode hopping in a single longitudinal mode over a wide temperature range AT (5-45 "C). The temperature coefficient of the wavelength in this range was 0.8 A deg", which was as small as that of the distributed feedback laser. At the extremes of this temperature range mode hopping occurred. The wavelength did not shift into the nearest neighbouring mode but into one which was separated by several mode spacings. An interference between the fundamental and higher-order transverse modes might be the underlying mechanism.
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