Structure and magnetic properties of sputtered thin films of Fe0.79Ge0.21Temperature dependence of the photoreflectance of a strained layer (001) In0.21Ga0.79As/GaAs single quantum wellWe have measured Schottky-barrier electroreflectance spectra of an lllo.79Gao.2IASo.s,P0.46 LPE layer at 81 K. Analysis of the spectra has enabled us to determine the interband reduced mass of the quaternary alloy together with the values of the band gap and spin-orbit splitting. The obtained reduced mass /-L = 0.033 mo.in agreement with the value calculated from interpolations of the accepted values for the related binary compounds.
The bandgap energy of InGaAsP quaternary alloy lattice-matched to InP has been precisely determined by electroreflectance (ER) measurements. The ER spectra show the typical low-field ER lineshape over the whole alloy composition range, and this has enabled us to determine the precise bandgap energy of the InGaAsP alloy easily. It was found that the bandgap energy E
g of the In1-x
Ga
x
As
y
P1-y
alloy lattice-matched to InP is written as E
g
=1.35-0.738·y+0.138·y
2 at room temperature as a function of the As composition y. We have also measured the photoluminescence spectra of the InGaAsP samples, and found that the peak energy of the photoluminescence spectrum, which is frequently used as a measure of the bandgap energy, is slightly different from the precise bandgap energy determined by ER measurements.
Deep impurity levels in InP LEC single crystals have been investigated by deep-level transient spectroscopy (DLTS) and photoluminescence (PL) measurements. The effects of heat treatment on DLTS and PL signals have been investigated, the results indicating that a deep impurity level whose emission activation energy is 0.42 eV is closely related to the well-known PL emission band at 1.1 eV. It seems that these DLTS and PL signals originate from a certain complex including P vacancies and defects, since some behaviours of these signals can be well explained by a configuration-coordinate model. Two other deep levels with emission activation energies of 0.31 and 0.60 eV have also been observed. The origin of these deep impurity levels might be due to native defects in the InP LEC crystals.
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