Exciton photoluminescence in strained and unstrained ZnSe under hydrostatic pressure

Tuchman, Judah A.; Kim, Sangsig; Sui, Zhifeng; Herman, Irving P.

doi:10.1103/physrevb.46.13371

Cited by 50 publications

(28 citation statements)

References 30 publications

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“…Pressure causes no strong changes in the width of the SA bands as long as the 4He medium is well annealed. As expected, we find that the 12 lines follow the ZnSe band gap; the small difference in shift for the two donor species (Table 2) is typical of results in ZnSe [49]. The SA bands respond to pressure quite differently than the 12 lines, requiring two pressure coefficients for each sample (denoted d E < / d P and dE'/dP) to describe their behavior.…”

Section: Energy (Ev)mentioning

confidence: 50%

Competition of Deep and Shallow Impurities in Wide‐Gap II‐VI Semiconductors under Pressure

Weinstein

Ritter

Strachan

et al. 1996

Physica Status Solidi (b)

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The effects of applied pressure on deep defects, shallow ++ deep competition, and related doping problems in 11-VI semiconductors are reviewed. Photoluminescence studies to 100 kbar (at 7 K) on high purity ZnSe, and on several ZnSe samples doped with 10l6 to 10" cm-3 C1, Ga, N, P, and As reveal striking differences between the pressure-shifts of broad-band features involving acceptor and/or donor deep states, and excitonic lines due to shallow band-edge states. The binding energies of observed deep acceptor states tend to decrease with pressure, suggesting that compression acts to destabilize these states against competing shallow hole levels. A deep donor level assigned to an excited state of donor-vacancyz,, complexes emerges from the electron continuum in n-type Gaand C1-doped samples at -25 to 28 kbar. This previously unknown state should not affect doping in ZriSel-zTe, alloys since it arises from existing compensation centers.

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Section: Energy (Ev)mentioning

confidence: 50%

Competition of Deep and Shallow Impurities in Wide‐Gap II‐VI Semiconductors under Pressure

Weinstein

Ritter

Strachan

et al. 1996

Physica Status Solidi (b)

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“…Figure 3 shows that all the observed PL and PLE peak positions shift to higher energy with compression [15]. The I 2 pressure shift is 6.2 6 0.2 meV͞kbar, very close to that of the ZnSe band gap ͑6.5 6 0.2 meV͞kbar͒ [16]. The faster-than-gap shifts of the V Zn ͑8.4 6 0.5 meV͞kbar͒ and A-center ͑10.4 6 0.5 meV͞kbar͒ PL bands suggest that the deep acceptor states (optical levels) involved in these DAP transitions become more shallow with pressure.…”

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confidence: 88%

Effects of Pressure on the Zn Vacancy in ZnSe: Essential Role of Lattice Relaxation for a BasicC3vDefect

Iota

Weinstein

1998

Phys. Rev. Lett.

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The photoluminescence (PL) and PL excitation (PLE) spectra of the isolated Zn vacancy ͑V Zn ͒ in ZnSe are measured under hydrostatic pressure to 50 kbar at 7 K. The PL band shifts with pressure, roughly 30% faster than the band gap. Compression decreases the Stokes shift, reflecting a reduction in the C 3y lattice relaxation around the V 2 Zn site. Defect-molecule calculations show that this arises from the dominance of spring-constant stiffening over increased Jahn-Teller coupling. We determine the V Zn configuration-coordinate diagram at high pressure. Compression deepens the energy of the V 2 Zn thermal level. [S0031-9007(98)07699-6] PACS numbers: 71.55.Gs, 62.50. + p, 78.55.Et Stokes-shifted photoluminescence (PL) bands resulting from recombination at strongly lattice-relaxed defects are common in semiconductors [1]. In ZnSe, such bands arise from, e.g., isolated Zn vacancies ͑V Zn ͒ [2], donorvacancy complexes (A centers) [1], and Se-site acceptors [3]. Although pressure experiments have been reported for a number of deep PL transitions [4,5], the results can be difficult to interpret in the presence of strong lattice relaxation [6]. Often, the pressure shifts of deep PL peaks are slower than that of the material's direct band gap [7], in agreement with the insensitivity to compression predicted for localized states by either Brillouin zone averaging [8] or tight binding models [9]. In contrast, recent experiments reveal that the deep PL bands in ZnSe due to P Se , As Se and the A centers of Ga and Cl shift with pressure substantially faster (ϳ2 to 6 meV͞kbar faster) than the band gap [10,11].This rapid pressure shift suggests that the pertinent deep levels [acceptors ϳ0.3 0.7 eV above the valence band edge (VBE)] become more shallow with pressure, a result that bears on p-type doping problems in II-VI materials [12,13]. However, the possible explanations of this behavior are problematic. Either (i) the VBE moves rapidly to higher absolute energy with pressurein disagreement with theory [14]; (ii) the deep acceptor states shift rapidly to lower energy (in fact, faster than the VBE by ϳ22 to 26 meV͞kbar)-despite strong localization; or (iii) the lattice relaxation at defect sites decreases with pressure-counterintuitive to the expected increase in electron-phonon coupling due to enhanced orbital overlap.To resolve these issues, we perform experiments and calculations that explore the influence of lattice relaxation on the pressure behavior of the PL and PL excitation (PLE) spectra of the V Zn center in ZnSe. This deep defect is prototypical. In the standard tight binding picture, the V Zn levels are delimiters for the bound states of deep defects on the Zn sublattice [7,9]. Its V 2 Zn charge state is subject to a strong C 3y Jahn-Teller distortion [2]. We present pressure data on the V Zn optical levels that can be understood only by taking explicit account of lattice relaxation changes. Considering the delimiting nature of the V Zn levels, our findings bear on a wide range of cation-substitutional localized ...

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“…The results are shown in Fig. 3, along with the known pressure dependence of PL features from thick ZnSe epilayers grown on GaAs substrates [11]. The pressure-induced energy shift of the optical transi- It is very interesting to note that the energy level of O in ZnSe determined here can be used to evaluate band-edge offsets between ZnTe and ZnSe.…”

Section: Methodsmentioning

confidence: 93%

Oxygen induced band‐gap reduction in ZnO_xSe_1−x alloys

Shan¹,

Walukiewicz

Ager

et al. 2004

Physica Status Solidi (b)

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The effect of alloying a small amount of ZnO with ZnSe on the electronic band structure has been studied. Optical transitions in MBE-grown ZnO x Se 1-x epitaxial films (0 ≤ x ≤ 0.0135) were investigated using photoreflectance and photoluminescence spectroscopies. The fundamental band-gap energy of the alloys was found to decrease at a rate of about 0.1 eV per atomic percent of oxygen. The pressure dependence of the band gap was also found to be strongly affected by the O incorporation. Both effects can be quantitatively explained by an anticrossing interaction between the extended states of the conduction band of ZnSe and the highly localized oxygen states located at approximately 0.22 eV above the conduction band edge.1 Introduction Highly mismatched semiconductor alloys (HMAs) in which a small fraction of constituent anion elements is replaced by elements with highly dissimilar properties have recently attracted considerable attention. The most extensively studied HMAs to date are III-N-V alloys. It has been found that the substitution of the group V element in group III-V compounds with small amounts of nitrogen leads to dramatic changes of the electronic properties, resulting in a reduction of the fundamental bandgap energy [1, 2], a significant increase in electron effective mass and a decrease in electron mobility [3][4][5], and the appearance of a new optical transition (E + ) from the valence band to the conduction band at the Γ point [6,7]. As one quantitative example, the incorporation of only one percent of nitrogen into GaAs induces a strikingly large reduction of 0.18 eV in the fundamental band-gap energy [8].The dramatic changes of the electronic properties have been well explained by a band anticrossing (BAC) model [6,9]. The anticrossing interaction between the extended conduction-band states of a semiconductor matrix and the highly localized electronic states introduced by the isoelectronic substitutional atoms with high electronegativity can be expressed as [6,9]

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Exciton photoluminescence in strained and unstrained ZnSe under hydrostatic pressure

Cited by 50 publications

References 30 publications

Competition of Deep and Shallow Impurities in Wide‐Gap II‐VI Semiconductors under Pressure

Competition of Deep and Shallow Impurities in Wide‐Gap II‐VI Semiconductors under Pressure

Effects of Pressure on the Zn Vacancy in ZnSe: Essential Role of Lattice Relaxation for a BasicC3vDefect

Oxygen induced band‐gap reduction in ZnO_xSe_1−x alloys

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Exciton photoluminescence in strained and unstrained ZnSe under hydrostatic pressure

Cited by 50 publications

References 30 publications

Competition of Deep and Shallow Impurities in Wide‐Gap II‐VI Semiconductors under Pressure

Competition of Deep and Shallow Impurities in Wide‐Gap II‐VI Semiconductors under Pressure

Effects of Pressure on the Zn Vacancy in ZnSe: Essential Role of Lattice Relaxation for a BasicC3vDefect

Oxygen induced band‐gap reduction in ZnOxSe1−x alloys

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Oxygen induced band‐gap reduction in ZnO_xSe_1−x alloys