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- 1. Advances in Science and Technology 46, 73 (2006) , Trans Tech Publications, Switzerland , “Electric-Field-Enhanced Thermal Emission from Osmium-Related”, M. Zafar Iqbal, A. Majid, A. Dadgar and D. BimbergDeep-level defects related with 5d transition metal, osmium (Os) have been studied in ntype GaAs. Os has been incorporated in epitaxial n-GaAs layers in situ, during growth by lowpressure metal-organic chemical vapour phase epitaxy (MOVPE) technique. Mesa p+nn+ junction diodes are fabricated for investigations by deep level transient spectroscopy (DLTS). Two deeplevel peaks, observed in majority carrier (electron) emission spectra, Os1 and Os2, show a significant shift in peak positions to lower temperatures with the applied junction reverse bias, demonstrating enhancement of the thermal emission rate by the junction electric field. Doublecorrelation DLTS (DDLTS) measurements have been employed for accurate quantitative investigations of the observed field dependence. However, in view of the relatively small concentration of the deep level Os1, this technique is found to yield reliable data only for the deep level corresponding to the dominant peak, Os2. Detailed data have been obtained on the field effect for Os2, extending over junction electric field values 3 x 106 V/m - 1.2 x 107 V/m. The measured emission rate signatures show a reduction of the thermal activation energy from 0.48 eV to 0.21 eV for Os2 over this electric field range. Analysis of the data in terms of the recent theoretical work on field dependence indicates that Os2 is associated with a substitutional Os donor. (Read more)
- 2. AIP Conf. Proc. 772, 147 (2005) , American Institute of Physics , “Deep levels in osmium doped p-type GaAs grown by metal organic chemical vapor deposition”, M. Zafar Iqbal, A. Majid, A. Dadgar, and D. BimbergResults of a preliminary study on deep level transient spectroscopy (DLTS) investigations of osmium (Os) impurity in p-type GaAs, introduced in situ during MOCVD crystal growth, are reported for the first time. Os is clearly shown to introduce two prominent deep levels in the lower half-bandgap of GaAs at energy positions Ev + 0.42 eV (OsA) and Ev + 0.72 eV (OsB). A minority-carrier emitting defect feature observed in the upper half-bandgap is shown to consist of a band of Os-related deep levels with a concentration significantly higher than that of the majority carrier emitting deep levels. Detailed data on the emission rate signatures and related parameters of the Os-related deep levels are reported. ©2005 American Institute of Physics (Read more)
- 3. J. Appl. Phys. 98, 083709 (2005) , American Institute of Physics , “Osmium impurity-related deep levels in n-type GaAs”, A. Majid, M. Zafar Iqbal, A. Dadgar and D. BimbergThe 5d transition-metal impurity, osmium, has been incorporated during the growth of n-type GaAs epitaxial layers using low-pressure metal-organic chemical-vapor deposition to characterize defect states associated with this heavy and, therefore, thermally stable dopant impurity.... (Read more)
- 4. Physica B 340, 358 (2003) , “Osmium related deep levels in n-type GaAs ”, M. Zafar Iqbal, A. Majid, A. Dadgar, D. BimbergDeep levels due to 5d transition metal, osmium (Os), in n-type GaAs epitaxial layers grown by metal-organic vapour-phase epitaxy are investigated using deep level transient spectroscopy (DLTS). Two clear and prominent peaks are observed in majority carrier (electron) emission spectra in GaAs:Os samples in addition to a weaker, broad feature at higher temperatures, which are absent in the Os-free, reference samples. The well-resolved, prominent peaks are attributed to deep levels associated with Os impurity having activation energies Ec−0.28 eV and Ec−0.41 eV at a junction electric field of not, vert, similar1.4×105 V/cm. Both of these peaks are found to be field dependent. Detailed data on emission rate signatures, apparent electron capture cross-sections and defect concentrations are reported for these levels. No Os-related deep level peaks could be clearly delineated in minority-carrier injection DLTS, at this stage, although some evidence is found for a low-energy deep level band. (Read more)
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