COMPOSITIONAL DEPENDENCE OF THE CONDUCTION-BAND EFFECTIVE-MASS OF INGAASP LATTICE-MATCHED TO INP

The conduction-band-edge effective masses in InGaAsP alloys have been determined for several different compositions covering the complete ra nge of alloys grown lattice-matched on InP. The effective mass is obta ined from far-infrared optically detected cyclotron resonance (ODCR). In contrast to previous experiments, the ODCR technique provides a dir ect method to determine the band-edge effective mass in undoped thin f ilms. Thus, a correction due to nonparabolicity effects is not require d. It is found that the experimental values are larger than the effect ive masses predicted from the five-band (k) over right arrow .(p) over right arrow calculation. We show that this discrepancy can be satisfa ctorily removed by the introduction of the effect of disorder-induced potential fluctuations which causes the wavefunction mixing between co nduction and valence bands. It is found that the strength of the poten tial fluctuations can be well described in terms of the Phillips's ele ctronegativity difference related to chemical disorder. In addition, t he dependence of the band-gap energy on alloy composition is determine d by photoluminescence measurements, and it also shows a nonlinear rel ationship.