Variation of GaN Valence Bands with Biaxial Stress: Quantification of Residual Stress and Impact on Fundamental Band Parameters

1996 ◽  
Vol 449 ◽  
Author(s):  
N. V. Edwards ◽  
S. D. Yoo ◽  
M. D. Bremser ◽  
M. N. Horton ◽  
N. R. Perkins ◽  
...  
Keyword(s):  
Accurate Determination ◽  
Nonlinear Behavior ◽  
Biaxial Stress ◽  
Energy Separation ◽  
Energy Position ◽  
Orbit Splitting ◽  
Spin Orbit Splitting ◽  
Valence Bands ◽  
Reflectance Data

ABSTRACTWe provide the widest estimate thus far of the range of tensile and compressive stress (−3.8 to 3.5 kbar) that GaN epitaxial material can withstand before relaxation occurs, and an unambiguous determination of the spin-orbit splitting Δso = 17.0 ± 1 meV for the material. These are achieved by analyzing 10K reflectance data for the energy separation of transitions between the uppermost valence bands and the lowest conduction band of wurtzitic GaN as a function of biaxial stress for a series of GaN films grown on both Al2O3 and 6H-SiC substrates. Our data explicitly show the nonlinear behavior of the excitonic energy splittings B-A and C-A vs. the energy position of the A exciton, which stands in contrast to the linear approximations used by previous workers analyzing material grown only on Al2O3 substrates. Further, the lineshape ambiguities present in GaN reflectance spectra that hindered the accurate determination of such excitonic energies have also been resolved by analyzing these data in reciprocal space, where critical point energies are determined by phase effects to an accuracy of ±0.5 meV.

New Evidence for the Second Conduction Band in 4H SiC

2017 ◽  
Vol 897 ◽  
pp. 250-253 ◽  
Author(s):  
Walter Klahold ◽  
Charles Tabachnick ◽  
Gabriel Freedman ◽  
Robert P. Devaty ◽  
Wolfgang J. Choyke
Keyword(s):  
Conduction Band ◽  
Energy Gap ◽  
Free Exciton ◽  
Epitaxial Films ◽  
Energy Separation ◽  
Orbit Splitting ◽  
Conduction Bands ◽  
Spin Orbit Splitting ◽  
New Evidence ◽  
Absorption Measurements

Differential absorption measurements were taken on ultra-pure boule pieces and epitaxial films of 4H SiC. The energy range of particular interest is from 3.40 eV to 3.52 eV. The free exciton energy gap associated with the second lowest conduction band at the M point in the Brillouin zone was determined to be EGX-2 = 3.4107 eV. This value is obtained from phonon assisted free exciton transitions involving the second conduction band measured in transmission with polarization E⊥c. The energy separation of the two lowest conduction bands is determined to be 144 ± 2 meV. Some replica peaks attributable to the spin orbit splitting in the valence band are also seen.

Temperature variation of energy gap values in CuGaSnSe4

1982 ◽  
Vol 60 (1) ◽  
pp. 10-15 ◽  
Author(s):  
S. Adan Lopez-Rivera ◽  
R. Gerald Goodchild ◽  
Owain H. Hughes ◽  
John C. Woolley ◽  
Brian R. Pamplin
Keyword(s):  
Temperature Variation ◽  
Energy Gap ◽  
Single Crystal Sample ◽  
Spin Orbit ◽  
Orbit Splitting ◽  
Crystal Sample ◽  
Energy Gaps ◽  
Spin Orbit Splitting ◽  
Valence Bands ◽  
D Orbitals

Measurements of reflectance as a function of temperature from 4 to 300 K have been made on a single crystal sample of CuGaSnSe4 using light polarised (a) perpendicular and (b) parallel to the c axis of the crystal. Values of the energy gaps EA, EB, and EC between the three valence bands and the conduction band have thus been determined as a function of temperature. The variation of these energy gaps with temperature has been fitted to the equation proposed by Manoogian and Leclerc, i.e., E0 − E = UTs + Vθ(coth (θ/2T) − 1). Values of spin–orbit splitting Δso and crystal field splitting Δcf have been determined and the temperature variation of these explained in terms of contributions from d orbitals to the valence band. Values of the various spin–orbit splittings and deformation potentials are discussed.

THE SUPPRESSION OF VITRINITE REFLECTANCE IN SOME NORTH WEST SHELF WELLS: BARROW-1, JUPITER-1 AND FLAMINGO-1

1992 ◽  
Vol 32 (1) ◽  
pp. 300 ◽  
Author(s):  
R.W.T. Wilkins ◽  
J.R. Wilmshurst ◽  
G. Hladky ◽  
M.V. Ellacott ◽  
C.P. Buckingham
Keyword(s):  
Organic Matter ◽  
Vitrinite Reflectance ◽  
Accurate Determination ◽  
Petroleum Exploration ◽  
Thermal Maturity ◽  
North West ◽  
The North ◽  
The Individual ◽  
Reflectance Data

The sediments of the North West Shelf pose several problems for the accurate determination of thermal maturity by vitrinite reflectance. There are some serious discrepancies between the results of different workers; in some wells there is a surprisingly small increase of reflectance with depth, and it is sometimes difficult to honour these data in thermal maturity modelling. There appear to be two major sources of error in the reflectance data. These are firstly, the effect known as 'suppression' of vitrinite reflectance, and secondly, the difficulty of identifying the vitrinite population in dispersed organic matter.These problems may be addressed by the fluorescence alteration technique which is closely related to vitrinite reflectance but has two special advantages. Firstly, it depends on an analysis of the fluorescence alteration response of a small representative population of organic matter in which the individual macerals need not be identified. Secondly, anomalous vitrinites with suppressed vitrinite reflectance are readily characterized, and the corrected equivalent reflectances determined.The technique has been tested on three North West Shelf petroleum exploration wells, Barrow-1, Jupiter-1 and Flamingo-1. Major discrepancies between measured and equivalent vitrinite reflectance appear to originate in part from the difficulty of identifying the vitrinite population in dispersed organic matter from marine sediments. There is also evidence of suppression of vitrinite reflectance in most samples from Barrow-1, in the Flamingo Group and Plover Formation of Flamingo-1, and in the upper part of the Mungaroo Formation of Jupiter-1.A model is proposed to facilitate the assessment of measured vitrinite reflectance data from Carnarvon or Bonaparte Basin wells. Suppression effects are likely to have influenced measured vitrinite reflectance results from wells for which the strongest data are obtained from the Lower Cretaceous fluvio-deltaic Barrow Group sediments or their equivalents.

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