Characterization of low-temperature molecular-beam-epitaxy grown GaBiAs layers

GaBiAs layers with Bi content reaching 8.4% are grown by MBE technique at low temperatures. All layers were of p-type with carrier densities ranging from 3 x 10(14) to 2 x 10(15) cm(-3) and resistivities exceeding 60 Omega cm. Energy bandgap of the gallium bismide alloys as determined from spectral measurements of the optical absorption, photoconductivity and photoluminescence decreases linearly with increasing Bi content. Optical pump-terahertz probe measurements made on these layers show that the carrier density dynamics is best described by a double-exponential decay. The shorter of the time constants corresponds to the electron trapping and the longer time constant corresponds to the trap emptying times. It has been found that the electron trapping cross-section is of the same order of magnitude as the corresponding parameter for As-antisite traps in LTG GaAs; therefore, it is reasonable to assume that As antisites play a significant role in carrier recombination processes in GaBiAs, too.