RELATION BETWEEN PHOTOLUMINESCENCE WAVELENGTH AND LATTICE MISMATCH IN METALORGANIC VAPOR-PHASE EPITAXY INGAAS/INP

The photoluminescence (PL) wavelength of high-purity 0.5-mum-thick metalorganic vapor-phase epitaxy In1-xGaxAs/InP was measured at room temperature (RT) as a function of composition. The relaxed mismatch of these coherently strained layers was between -0.25% and +0.13%, corresponding to x = 0.503 - 0.448. The composition was determined by x-ray diffraction (XRD) using a four-crystal monochromator. Extremely narrow XRD linewidths as a function of layer thickness are reported. The PL peak wavelength lambda(p) at RT of exactly lattice-matched InGaAs is 1668 nm, corresponding to a band gap E(g) = 731 meV. The bowing parameter of the strain-free E(g)(x) relation is c = -0.494. The measured lambda(p) vs x relation agrees well with the strain-free E(g)(x) corrected by the hydrostatic part of the strain energy. From line-shape analysis of RT and 77 K PL spectra it is found that the spectra of strained layers contain two lines in accordance with the valence band splitting under uniaxial strain. The conditions for a reliable determination of the compositional homogeneity of large InGaAs wafers by a mapping of lambda(p) are given; e.g., a variation DELTA(x) = 8.7 X 10(-3) over a 2 in. wafer is found.