Photoluminescence (PL) and selective pair luminescence (SPL) techniques were used to evaluate a large number of GaAs crystals. It was found that the results of these photoluminescence measurements, combined with data on carbon concentration obtained by local vibrational mode absorption spectroscopy, make possible an analysis of shallow impurities. Their relative concentrations were compared from seed to tail and from crystal to crystal and correlated to material resistivity. Impurities segregation in a crystal was analysed. Results of polariton line shape and intensity analysis were used in surface-related studies. Advantages of using both PL and SPL as a routine production analytical technique will be enhanced when the equipment for two-dimensional mapping of a whole GaAs wafer is completed.
We have used a series of all-optical measurements to determine shallow acceptor, shallow donor, and midgap donor (EL2) concentrations. The validity of these measurements was then tested by comparing the predicted electron density to the measured Hall density. Resonant pumping of the first excited state of the polariton sharpened the photoluminescence spectrum sufficiently to allow a reliable measurement of the shallow donor to acceptor ratio. The absolute shallow acceptor, donor, and EL2 concentrations were determined by a series of absorption and luminescence measurements. The Fermi level and hence the carrier concentration was then deduced using the three-level model of semi-insulating behavior.
A number of optical techniques that can be used for the nondestructive characterization of semi-insulating GaAs are described. These techniques include regular photoluminescence, photoluminescence excitation spectroscopv, selective donor-acceptorpair luminescence, electronic Raman scattering, and local vibrational mode absorption for the identification and concentration determination of acceptors. For donors, magneto-photoluminescence can determine the chemical identity and relative concentration of the shallow donors, while for the important deep donor EL2, absorption and bleaching experiments determine the neutral EL2 concentration. The utility of these techniques for routine and reliable characterization of production and developmental GaAs wafers is discussed. The possible extension of these techniques to spatially resolved 2D mapping of GaAs wafers is also discussed.On dCcrit des mtthodes optiques utilisables pour la caractCrisation non-destructive du GaAs semi-isolant. Ces mtthodes incluent la photoluminescence conventionnelle, la spectroscopie avec excitation de photoluminescence, la luminescence sClective de paires donneurs-rkcepteurs, la diffusion Raman Clectronique et I'absorption des modes de vibration locaux pour I'identification et la determination de la concentration des rkcepteurs. En ce qui concerne les donneurs, la magnCto-photoluminescence peut dCterminer 1'identitC chimique et la concentration relative des donneurs lCgers, alors que pour l'important donneur EL2, des expkriences d'absorption et de saturation dtterminent la concentration des EL2 neutres. On discute I'utilitC de ces mCthodes pour la caractCrisation routinikre et fiable de gaufrettes de GaAs de production et de dCveloppement. On traite aussi de I'extension possible de ces mtthodes pour la caractCrisation bidimensionnelle des gaufrettes de GaAs.[Traduit par la revue]Can. J. Phys. 67,242 (1989)
We have developed a whole-wafer, low-temperature imaging system for making absorption and photoluminescence maps of wafers up to 100 mm (4 in) in diameter. The cryostat requires no cryogens and can maintain a temperature of 15 K in the sample chamber indefinitely. He gas provides the thermal contact with the samples, allowing rapid (15 min) interchange of samples. The transmitted or emitted light from the wafer is imaged on a CCD (charge-coupled device) camera rather than using a raster scanning mechanism. The resultant parallel collection advantage allows images to be acquired in much less time. The system is ideally suited for the routine characterization of large numbers of wafers. This apparatus has been used to map the neutral EL2 concentration and near gap photoluminescence efficiency for a number of semi-insulating GaAs wafers.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.