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By the techniques of far-infrared optically detected cyclotron resonance and magnetophotoconductivity, we have performed cyclotron-resonance measurements on relaxed In Ga& As epitaxial layers with a wide range of composition. The measured electron effective mass as a function of indium composition has been analyzed with the five-band k p calculation. It is found that the effect of disorder-induced conductionvalence-band mixing must be included in order to resolve the discrepancy between the results of the k p theory and experiments. The linewidths of cyclotron resonance and photoluminescence as a function of alloy composition have also been studied. Comparing with the measurement of doublecrystal x-ray diffraction, we point out that the cyclotron-resonance and photoluminescence signals in In"oa& As alloys are dominated by the dislocation scattering. In addition, we show that the quality of a ternary epilayer is not only influenced by the lattice mismatch; the surface migration lengths of the cation atoms in the initial growth stage also play a very important role.

The enhancement of light extraction from Si(0.5)Ge(0.5)/Si multiple quantum wells (MQWs) with nanowall structures fabricated by electron cyclotron resonance (ECR) plasma etching is presented. It is shown that the ECR plasma treatment does not damage the crystalline quality. At a driving current of 5.5 × 10(6) A m(-2), the light output intensity of the MQWs with nanowall structures shows an enhancement of about 50% compared with that of the original MQWs. In addition to the enhanced light extraction, the improved optoelectronic properties are also attributed to the strain relaxation in nanowall structures.

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