摘要:

AbstractUniaxial strain, having a larger number of irreducible components, yields in principle more information than its hydrostatic counterpart. It has, however, the drawback that its magnitude is limited by sample fracture. We discuss the methods of application of uniaxial stress to solid samples for the purpose of performing spectroscopic measurements. We then present some of the highlights of such measurements, concerning phonons and electronic states in semiconductors.

ISSN:0370-1972    

DOI:10.1002/pssb.2221980103

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe dielectric constants of semiconductors under pressure are derived fromab initiocalculations of the complex dielectric functions ε(ω). The pressure coefficient of the refractive index is negative for most tetrahedrally bonded compounds and trends are explained within a simple model. Gap deformation potentials as well as “absolute” band edge deformation potentials are derived, and the pressure dependence of the electronic structure of superlattices is discussed. Examples from the group III‐V, in particular nitrides, and II‐VI (ZnS, ZnS/ZnSe) compounds illustrate these investigations. Also, less conventional semiconductors, β‐FeSi2and ε‐FeSi, are examined. Strong electron correlation effects limit the validity of LDA theory in these cases. It is suggested that experimental pressure studies can shed new light on the properties of K

ISSN:0370-1972    

DOI:10.1002/pssb.2221980104

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractStimulated emission of far‐infrared radiation from uniaxially compressed p‐Ge in strong electric fields is shown to be due to population inversion of strain‐split acceptor levels. A peak corresponding to the optical transitions between split‐off and ground acceptor states is found in the spectrum of stimulated emission. A strong frequency tuning by stress due to the pressure dependence of the energy splitting of these states is obtained. The inversion takes place as the split‐off acceptor state is in the valence band

ISSN:0370-1972    

DOI:10.1002/pssb.2221980105

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe effect of hydrostatic pressure (P) on the k = 0 conduction band mass m 0*(P) in lightly Si‐doped GaAs is studied by far‐infrared magnetospectroscopy. The electron cyclotron resonance (CR) at (T= 17 K), and the 1s‐2p+absorption of Si donors (atT= 4.2 K), are measured up to 40 kbar under fields of 6 to 9 T by Fourier transform and laser magnetotransmission techniques. DX‐center trapping is avoided by visible illumination. A double‐bellows diamond‐anvil cell and 36 mm bore magnet enable in situP‐B‐Ttuning. The slopes dE/dBfor the CR and 1s‐2p+peaks decrease with pressure in accordance with effective mass theory, with no sign of strong deepening for the Si 1s(Γ) state. We find m 0*(P)/m 0*(0) = 1 + (6.1 ± 0.3) × 10−3P– (1.3 ± 0.5) × 10−5P2(Pin kbar) from the CR data, after correcting for nonparabolicity via an effective two‐band k.p model. This agrees well with prior results limited to 17 kbar, and extends the measurement of

ISSN:0370-1972    

DOI:10.1002/pssb.2221980106

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractWe have measured time‐resolved photoluminescence (TR‐PL) spectra in ordered and disordered Ga0.5In0.5P alloys at 12 K and at pressures up to 3 GPa to investigate the characteristics of the main broad PL spectrum at ≈︁1.91 eV in nominally ordered alloys. At normal pressure, unlike the disordered alloy, the PL‐decay profiles for the ordered alloys change remarkably for small changes in detection energy. This indicates the presence of adjacent overlapping emissions of different nature. Together with the prolonged nonexponential decay curves, a gradual red‐shift of the low‐energy peak with delay time is observed for the first time, indicating spatially indirect recombinations. With increasing pressure, the constituent emissions shift toward higher energies at rates slightly smaller than that for the disordered alloy. At 3 GPa, the PL decay appears to be insensitive to the detection energy, and a faster deca

ISSN:0370-1972    

DOI:10.1002/pssb.2221980107

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractMeasurement of the pressure dependence of the direct bandgap of a tetrahedral semiconductor shows a pronounced sublinearity. This is explained by the stiffening of the lattice under pressure, so that if the pressure is converted into change of lattice constants using a suitable equation of state, the relation between bandgap and lattice constant is found to be linear within experimental (and theoretical) error. However, fitting to the pressure data, many authors use a parabolic equation,Eg(P) =Eg(0) +aP–bP2. We show that this gives a systematic error in the determination of the linear term a which increases with the pressure range of the experiment. GaAs provides a typical example of the systematic error. We find that the true linear pressure coefficient of GaAs is near 11.5 meV/kbar in agreement with the recent low‐pressure measurement of Perlin et al. rather than the long‐accepted value of 10.7 meV

ISSN:0370-1972    

DOI:10.1002/pssb.2221980108

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThis paper reviews experimental studies on the magnetophotoluminescence in diluted magnetic semiconductors Cd1−xMnxSe with x = 0.01, 0.05, 0.10, and 0.25 and Cd1−xCoxSe with x = 0.012 at 1.4 and 4.2 K under hydrostatic pressures up to 2 GPa. The studies focus attention to the pressure dependence of the magnetic dichroism of the 1 s exciton state under magnetic fields of 0 to 27 T. Pressure strengthens the exciton‐Mn(Co) and Mn(Co)‐Mn(Co) exchange interactions. An analysis of these results in terms of the kinetic exchange theory shows that the on‐site Coulomb energyUand the chargetransfer energy Δ are reduced markedly b

ISSN:0370-1972    

DOI:10.1002/pssb.2221980109

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractTwo‐photon spectroscopy has been used to determine the pressure dependence of band‐structure parameters such as band gap, exciton binding energy, biexciton binding energy, exchange energy, and Luttinger parameters. Compared to linear spectroscopy it yields not only a higher precision, but is often able to determine a larger number of parameters. Results are presented for ZnTe and CuCl nanocrystals in a LiCl mat

ISSN:0370-1972    

DOI:10.1002/pssb.2221980110

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractPhotoluminescence experiments on 6H‐SiC doped with nitrogen have been performed at low temperature (T= (29 ± 2) K) under hydrostatic pressure up to 5 GPa. The pressure coefficients of the S0, R0, P0, S02, and R02emission lines related to the neutral nitrogen donor bound excitons were determined. The pressure coefficient of the indirect gap of 6H‐Sic deduced from the P0line turns out to be +2.0 meV/GPa. Nonrelativistic band structure calculations within the density‐functional theory based on the local density approximation are used to calculate the pressure coefficients of the indirect band gaps of the 6H, 4H, and 3C SiC polytypes. The comparison with available experimental data shows good agreement with the theoretical r

ISSN:0370-1972    

DOI:10.1002/pssb.2221980111

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractIn this paper we present pseudopotential LDA calculations using a plane wave basis set. We investigate the structure of Ca3AsN and Ca3PN and consider its pressure dependence. Between the structures considered no phase transitions were found for positive pressures. Experimentally Ca3AsN and Ca3PN were found to have an orthorhombic structure which corresponds to a distorted cubic structure. Also theoretically this orthorhombic structure was found to be energetically the most favourable. Its corresponding lattice constants are in good agreement with the experimental data. Besides the lattice constants, the bulk moduli and its pressure derivatives we also calculate the electronic bandstructure.

ISSN:0370-1972    

DOI:10.1002/pssb.2221980112

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY