Non‐Γ Deep Levels and the Conduction Band Structure of Ga1−xAlxAs Alloys

Saxena, Ashok Kumar

doi:10.1002/pssb.2221050240

Cited by 90 publications

(17 citation statements)

References 26 publications

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“…If this model is true, then it should be possible to observe electron transfer to the high density of states L minima in n-GaAs and much more easily in GaAlAs where the subband separation for direct band gap material is expected to decrease with alloy composition. This is indeed true as already reported by the author elsewhere [16] from high temperature Hall measurements. These results yielded a sub-band energy separation of 0.285 eV in GaAs, which is almost the same as found in the present work.…”

Section: Analysis and Discussionsupporting

confidence: 75%

Defect Levels in n-Type Gallium Arsenide and Gallium Aluminum Arsenide Layers

Saxena

2001

phys. stat. sol. (a)

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Capacitance-voltage/time measurements have been made on Au-Schottky barrier diodes to LPE, VPE, bulk, OMVPE-GaAs, GaAlAs and MBE-GaAs/GaAlAs quantum wells to detect and characterize deep levels. LPE-GaAs was-grown by varying the degree of melt under-and super-saturation to study the effect on traps. Cylinder-piston assembly and Bridgman anvil systems were employed to observe the emission of carriers from deep levels up to a pressure of 50 Â 10 8 Pa. The effect of annealing on traps in VPE-GaAs has also been investigated. It has been shown that emission from the 0.83 eV (EL-2) level in GaAs is not dependent on electric field in the range of about 60-125 kV/cm. The energy pressure coefficient of this level in GaAs has been measured as 4.0 Â 10 8 meV/Pa by extending measurements, for the first time, to 15 Â 10 8 Pa. From emission studies at 50 Â 10 8 Pa, it has been shown that the level EL-2 is coupled to the L minima and the G-L energy separation of 0.282 eV accounts for most of the experimental data. The 0.83 eV level has also been found to exist in LPE-GaAs and it has been concluded that Ga vacancy and As Ga antisite defect complex are responsible as the most likely source of its origin. It has been concluded that the absolute position of the level in the band gap remains almost invariant with pressure and that there is no need to assume a pressure dependent Franck-Condon shift. However, for a similar level found in GaAs/GaAlAs MBE quantum wells, the energy pressure coefficient has been measured to be as high as (13.8 AE 0.8) Â 10 8 meV/Pa. In some samples, 0.83 and 0.76 eV electron levels exist together, clearly showing that these are two different levels. The 0.64 eV hole trap level has not only been found in LPE-GaAs, GaAlAs, heat treated VPE but also in 'as-grown' VPE-GaAs. The present results have discounted the pure Ga and As vacancy model for the 0.83 and 0.64 eV levels in VPE and LPE-GaAs, respectively. We attribute the 0.64 eV hole level to a Ga vacancy-Cr complex.

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Section: Analysis and Discussionsupporting

confidence: 75%

Defect Levels in n-Type Gallium Arsenide and Gallium Aluminum Arsenide Layers

Saxena

2001

phys. stat. sol. (a)

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“…[12]. Bowing parameters for the X-valley and L-valley gaps in Al x Ga 1−x As were determined using electrical measurements in combination with a theoretical model by Lee et al [1,4] and Saxena [21] as well as empirically by Casey and Panish [22]. These results and photoluminescence excitation spectroscopy data [23] support a E L Γ band-gap bowing parameter that is almost equal to zero.…”

Section: Resultsmentioning

confidence: 73%

Effects of hydrostatic pressure and temperature on electronic band parameters in AlxGa1?xAs

Boucenna

Bouarissa

2005

Czech J Phys

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Influence of hydrostatic pressure and temperature on electronic band parameters for zinc-blende AlxGa1−xAs was investigated by means of pseudopotential calculations. The agreement between our results and the available experimental data is generally satisfactory. Our results showed that the effect of pressure leads to a decrease of the crossing point and the optical bowing parameter. However, the temperature effect was found to be insignificant on both crossing point and bowing parameter.PACS : 71.20.Nr

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“…[1][2][3][4] However, the results from these studies are not totally consistent with each other. Our results agree best with the conductivity findings by Lee et al, which are plotted in Fig.…”

mentioning

confidence: 57%

“…In particular, parameters of the Al x Ga 1Ϫx As band structure have been determined from a variety of measurements, including photoresponse, 1 optical transmission and photoluminescence, 2 variation of Hall electron concentration with temperature, 3 and variation of electrical conductivity with temperature. 4 However, there is some uncertainty about the exact positions of ⌫, L, and X band edges, especially in the indirect band gap regime.…”

Section: Introductionmentioning

confidence: 99%

Mapping of AlxGa1−xAs band edges by ballistic electron emission spectroscopy

Cheng

Collins

McGill

1997

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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We have employed ballistic electron emission microscopy ͑BEEM͒ to study the energy positions in the conduction band of Al x Ga 1Ϫx As. Epilayers of undoped Al x Ga 1Ϫx As were grown by molecular beam epitaxy on conductive GaAs substrates. The Al composition x took on values of 0, 0.11, 0.19, 0.25, 0.50, 0.80 and 1 so that the material was examined in both the direct and indirect band gap regime. The Al x Ga 1Ϫx As layer thickness was varied from 100 to 500 Å to ensure probing of bulk energy levels. Different capping layers and surface treatments were explored to prevent surface oxidation and examine Fermi level pinning at the cap layer/Al x Ga 1Ϫx As interface. All samples were metallized ex situ with a 100 Å Au layer so that the final BEEM structure is of the form Au/capping layer/Al x Ga 1Ϫx As/bulk GaAs. Notably we have measured the Schottky barrier height for Au on Al x Ga 1Ϫx As. We have also probed the higher lying band edges such as the X point at low Al concentrations and the L point at high Al concentrations. Variations of these critical energy positions with Al composition x were mapped out in detail and compared with findings from other studies. Local variations of these energy positions were also examined and found to be on the order of 30-50 meV. The results of this study suggest that BEEM can provide accurate positions for multiple energy levels in a single semiconductor structure.

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Non‐Γ Deep Levels and the Conduction Band Structure of Ga_1−xAl_xAs Alloys

Abstract: Es wird gezeigt, daS in Gal-,AI,As mit Zusammensetzungen im Bereich 0,19 l) Mappin Street S1 3JD, Sheffield, Great Britain.

Cited by 90 publications

References 26 publications

Defect Levels in n-Type Gallium Arsenide and Gallium Aluminum Arsenide Layers

Defect Levels in n-Type Gallium Arsenide and Gallium Aluminum Arsenide Layers

Effects of hydrostatic pressure and temperature on electronic band parameters in AlxGa1?xAs

Mapping of AlxGa1−xAs band edges by ballistic electron emission spectroscopy

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