Evidence for highly localized states with a symmetry of substitutional donors which enter the gap of GaAs at high hydrostatic pressure

Dmochowski, J. E.; Wang, P D; Stadling, R A

doi:10.1088/0268-1242/6/2/010

Cited by 17 publications

(3 citation statements)

References 19 publications

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“…In addition to the shallow state these impurity centers also possess a deep state. [6][7][8] Application of UV and visible light at low temperatures results in disappearance of the absorption peak corresponding to the deep electronic state and an infrared absorption band associated with the occupation of the metastable shallow state. In other words, the electrons occupying the deep state are lifted due to photoexcitation to the shallow state.…”

Section: Introductionmentioning

confidence: 99%

Electronic and optical properties of cadmium fluoride: The role of many-body effects

Cappellini

Furthmüller²,

Cadelano

et al. 2013

Phys. Rev. B

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Electronic excitations and optical spectra of CdF2 are calculated up to ultraviolet employing state-of-the-art\ud techniques based on density functional theory and many-body perturbation theory. The GW scheme proposed\ud by Hedin has been used for the electronic self-energy to calculate single-particle excitation properties as energy\ud bands and densities of states. For optical propertiesmany-body effects, treated within the Bethe-Salpeter equation\ud framework, turn out to be crucial. A bound exciton located about 1 eV below the quasiparticle gap is predicted.\ud Within the present scheme the optical absorption spectra and other optical functions show an excellent agreement\ud with experimental data. Moreover, we tested different schemes to obtain the best agreement with experimental\ud data. Among the several schemes, we suggest a self-consistent quasiparticle energy scheme

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Section: Introductionmentioning

confidence: 99%

Electronic and optical properties of cadmium fluoride: The role of many-body effects

Cappellini

Furthmüller²,

Cadelano

et al. 2013

Phys. Rev. B

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“…A likely origin for these barrier traps is nominal levels of Se donors (on As sites). Se is a known residual impurity in MBE grown GaAlAs, and there is evidence that its X-associated state is non-metastable and has a binding energy of 100 meV (or about 60 meV below the X-level of Si donors in the GaAlAs system) [3,32]. Thus, the low fall-off pressures for ne Q W (Fig.…”

Section: Fir Magnetospectroscopy Of Cr D 0 and D-mentioning

confidence: 99%

“…These two facts of nature conspire against employing standard clamp diamond-anvil cells (DACs), in which it is extremely difficult to achieve pressure resolution and repeatability of less than a few kbar. Since clamp DACs are convenient for inserting into the restricted geometry of cryogenic FIR magnetooptical experiments, they have often been used for such studies in the past [2][3][4][5]. However, without in situ tuning, it becomes largely a matter of luck to detect the many fascinating resonant and anticrossing interactions that are possible in semiconductors.…”

Section: Introductionmentioning

confidence: 99%

High-Pressure Studies of Semiconductors in the Far-Infrared: Donor States in Quasi-2D

et al. 2000

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We review recent experimental advances by the Buffalo group in performing far-infrared magnetospectroscopy under he tuning of applied high hydrostatic pressure. Experiments are reported for the effects of pressure on Si donors in modulation doped GaAs/AlGaAs quantum wells. We clearly observe pressure-mediated competition between free (i.e., Landau level) and bound electron states -the latter arising from both neutral (D 0 ) and charged (D -) donor species. With increasing pressure, there is a progression of the observed spectra from being dominated by cyclotron resonance and the D -singlet (or singlet-like bound magnetoplasmon) transitions, to showing the D0 is →2p+ line. The main reason for this evolution is the decrease in electrons due to the crossover of the Si levels associated with the F (well) and X (barrier) conduction minima. Indeed, for pressures above 30 kbar the Γ(well)-X(barrier) crossover quenches all the transitions. However, we find strong evidence that electrons are independently lost to a trap, which becomes active several kbar below this crossing. A possible candidate for this trap is residual Se impurities in the barriers. We present the results of detailed numerical calculation which are found to agree very well with the measured field dependencies of the cyclotron resonance, D0 and D -transition energies. In the sample with the highest doping, a new transition is observed for fields and pressures above 7.5 T and 5 kbar. Reasons for this apparent anomaly are discussed.

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Spatial correlation effects in the charged impurity distribution on the electronic properties of δ‐doped structures

Stadt

Koenraad²,

Shi

et al. 2003

Physica Status Solidi (b)

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Dedicated by the coauthors to Professor Jozef T. Devreese on the occasion of his 65th birthday PACS 71.55. Eq, 73.50.Dn, 73.63.Hs In this paper we will show that the δ-doped GaAs/AlGaAs/GaAs quantum barrier is an ideal system to study deep centers in narrow doping layers with high doping density. By varying the Al content in the barrier, the distance between the Fermi-level and the deep level can be tuned and therefore the number of populated states. By applying hydrostatic pressure this number can be further increased. Our measurements show that in these δ-doped barrier structures electrons are trapped under hydrostatic pressure and that the quantum mobility is enhanced. This mobility enhancement can be explained by MC calculations which include the effect of the spatial correlation of the charge distribution when the deep state is the DX center and has a negative charge state. The fact that we do not observe a PPC effect or a significant change in the mobility after illumination at high pressure suggest that the Fermi-level is pinned by a non-metastable deep state like the A 1 state or that the DX center is modified.1 Introduction The idea of positioning individual atoms on a surface is very appealing and has many futuristic applications other than a 5-atom font size [1]. Using STM atoms can be moved around and placed on the surface in any configuration. Thus we can in principle create an artificial lattice. Especially in the semiconductor field this is an attractive concept because ordering of the doping atoms is expected to increase the electrical activity [2], reduce dopant fluctuations [3] and increase the carrier mobility [4]. However for practical applications too many atoms are involved thus the ordering of impurity atoms should be self-assembling. This can be accomplished by using a modified substrate surface, which has sites to which doping atoms preferentially go. At high enough growth temperatures the impurity atoms are allowed to diffuse to these sites. This technique has been applied to reconstructed surfaces [2,5] and misaligned substrates [6]. Most of these studies were concerned with structural properties and some with the consequences of such ordering on the electronic properties [7]. These growth studies are however difficult and require a lot of samples. There is fortunately a different approach to study spatial correlation effects by obtaining ordering in the charge distribution of randomly ordered impurity atoms. This ordering cannot be as large as a full spatial ordering introduced during growth, but the degree of ordering can be changed within one structure. Such ordering in the charge distribution can be obtained using the DX state associated with the Si donor in GaAs. By applying hydrostatic pressure electrons are trapped in these states. In current models this donor state is either neutral [8] or negatively [9] charged. Thus when DX centers are populated we have a so-called multi-valence system with either positively charged and

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Evidence for highly localized states with a symmetry of substitutional donors which enter the gap of GaAs at high hydrostatic pressure

Cited by 17 publications

References 19 publications

Electronic and optical properties of cadmium fluoride: The role of many-body effects

Electronic and optical properties of cadmium fluoride: The role of many-body effects

High-Pressure Studies of Semiconductors in the Far-Infrared: Donor States in Quasi-2D

Spatial correlation effects in the charged impurity distribution on the electronic properties of δ‐doped structures

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