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Epitaxial layers of p-GaAs grown on p+-GaAs substrates by low-pressure metal organic chemical vapor deposition have been investigated using deep level transient spectroscopy (DLTS). One dominant peak and other relatively small peak, corresponding to deep levels at Ev+0.55 eV and Ev+0.96 (low field energies), respectively, have been observed in the lower half of the band gap. Investigation with double-correlation DLTS reveals that the measured thermal emission rate of holes from the dominant level is strongly dependent on the junction electric field. Detailed data on this field enhancement have been analyzed in terms of different available theoretical models. The hole capture cross section for the dominant deep level has been found to be temperature dependent. Detailed data on the temperature dependence of the hole capture cross section have been interpreted in terms of the multiphonon carrier capture mechanism, yielding a capture barrier of 0.11 eV. In order to get deeper insight into the nature and origin of these inadvertent (intrinsic) defects, thermal annealing behavior of these levels has also been studied. Analyses of field dependence and hole capture data, in combination with the annealing study, suggest that the dominant level is associated with an arsenic-antisite (AsGa) defect. Probable association of this dominant level with the doubly charged state of the well-known EL2 defect has been discussed in detail. [ABSTRACT FROM AUTHOR]

Investigations of the alpha particle irradiation-induced defects in low-pressure metal-organic chemical-vapor deposition grown p-GaAs have been carried out. By employing deep-level transient spectroscopy, at least seven radiation-induced deep-level defects have been observed in the lower half of the band gap in the temperature range of 12-475 K. Double-correlation deep-level transient spectroscopy measurements show three prominent levels: two known radiation-induced levels namely, Hα1 and Hα5, and one inadvertent center HSA, present before irradiation, to exhibit a significant dependence of thermal emission rate on the junction electric field. For Hα1 and HSA the field-enhanced emission data are well fitted with a Poole-Frenkel model, using a three-dimensional square-well potential with radius r=3.2 and 1.43 nm, respectively. The field effect for Hα5 has been explained by a square-well potential in combination with a phonon-assisted tunneling process. Detailed data on the carrier capture cross section for all three levels have been obtained. The hole capture cross section for the levels Hα1 and Hα5 are found to be temperature independent, while for HSA, the hole capture data show a dependence on temperature. The dependence of hole capture cross section of HSA on temperature has been explained in terms of multiphonon capture mechanism, yielding a capture barrier of 0.13 eV and σ(∞)=1.5×10-14 cm2. These analyses lead us to conclude that the levels Hα1 and HSA are associated with a charged center, while the level Hα5 is most likely a substitutional defect in GaAs. [ABSTRACT FROM AUTHOR]

Abstract: Irradiation of p-GaAs grown by low-pressure metal-organic chemical-vapor deposition (LP-MOCVD) with α-particles from the 241Am source has been performed at room temperature. At least seven radiation-induced deep-level defects at energy positions E v+0.09eV, E v+0.11eV, E v+0.16eV, E v+0.24eV, E v+0.32eV, E v+0.42eV, and E v+0.77eV were detected in the lower-half of the band gap, using deep-level transient spectroscopy (DLTS), while no radiation-induced defects were observed in the upper-half band gap (minority carrier injection spectrum). The DLTS signatures of the radiation-induced defects are compared with the previously reported defects introduced in α-irradiated p-GaAs grown by molecular beam epitaxy (MBE). It has been observed that while four of these deep levels are similar to those found in α-irradiated MBE grown p-GaAs, three levels at E v+0.32eV, E v+0.42eV, and E v+0.77eV observed in our MOCVD material were not detected in MBE material. Data on the introduction rates and other characteristics of the radiation-induced defects are presented. [Copyright &y& Elsevier]

Abstract: A preliminary study of growth interruption effects on the GaAs/AlGaAs layers is reported. Deep level transient spectroscopy (DLTS) is performed on Al Schottky barrier devices fabricated on Si-doped, isotype GaAs/Al0.78Ga0.22As heterostructures grown by molecular beam epitaxy (MBE), both with (200s) and without, growth interruption. Our spectra extending from ∼15 to 300K show four peaks corresponding to deep level defects with thermal activation energies (E A): 0.09, 0.32, 0.42 and 0.52eV, which are detected in both types of samples (close to and) above liquid nitrogen temperature, although with different relative concentrations. Comparison with reported work on GaAs/Al x Ga1− x As samples with different compositions (x) shows that latter two of these deep levels are counterparts of the levels, P3–P4, earlier observed in MBE grown Al x Ga1− x As materials with Al content different than that used here. However, the deep level spectra of our samples show dramatic differences for the growth interrupted and uninterrupted samples in the temperature range below 77K. Whereas the samples prepared without growth interruption show a prominent, hitherto unobserved, positive (majority carrier emission) peak, P0 (E A=0.029eV), with shoulders on both higher and lower temperature flanks, the samples with growth interruption show a pronounced negative peak, apparently corresponding to a deep level with E A=0.031eV, in the same temperature region, under similar measurement conditions. The deep-level characteristics, including emission rate signatures and apparent capture cross-sections, are determined for the observed features using the thermal emission rate data. Some interesting additional features related to depth profiles of deep levels, bias effects and charge-induced metastability effects are also reported. [Copyright &y& Elsevier]