Showing papers by "Eric Tournié published in 2000"
TL;DR: In this article, a series of low-temperature photoluminescence and reflectivity spectroscopies were used to locate precisely the direct-to-indirect band-gap crossover at $x=0.70.
Abstract: We have investigated by low-temperature photoluminescence and reflectivity spectroscopies a series of ${\mathrm{Zn}}_{1\ensuremath{-}x}{\mathrm{Be}}_{x}\mathrm{Se}$ alloys with x up to 0.70. This allows us to locate precisely the direct-to-indirect band-gap crossover at $x=0.46\ifmmode\pm\else\textpm\fi{}0.01.$ We demonstrate that above this composition the indirect band gap corresponds to a $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\Gamma}}X$ transition. By extrapolation we determine the $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\Gamma}}X$ band gap of BeSe at $3.75\ifmmode\pm\else\textpm\fi{}0.1\mathrm{eV}.$ Finally, we find a bowing parameter $b=0.97\mathrm{eV}$ for the $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\Gamma}}\ensuremath{\Gamma}$ direct band gap in the whole composition range. For $xl~0.60,$ this band gap increases linearly with the Be content at a rate of 23 meV/% Be.
45 citations
TL;DR: In this article, as-grown Ga1−xInxNyAs1−y/GaAs quantum-well heterostructures (QWHs) prepared by solid-source molecular-beam epitaxy (SS-MBE) were investigated.
Abstract: We have investigated as-grown Ga1−xInxNyAs1−y/GaAs quantum-well heterostructures (QWHs) prepared by solid-source molecular-beam epitaxy (SS-MBE) We show that the QWH properties appear to depend strongly on the growth technique and that SS-MBE emerges as a technique of choice for growing these QWHs We demonstrate photoluminescence emission at wavelength as long as 143 μm at 295 K, and up to 168 μm at 10 K This shows that development of 155 μm optoelectronics based on the Ga1−xInxNyAs1−y/GaAs materials system may now be reasonably thought of
42 citations
TL;DR: In this paper, the P-related shallow-acceptor level is the shallowest acceptor ever detected in ZnSe with activation energy of 2.791 eV and a series of excited states of this acceptor reveals that it behaves like all substitutional acceptors.
Abstract: Phosphorus-implanted and plasma-doped ZnSe epitaxial layers grown by molecular-beam epitaxy are studied through photoluminescence (PL), selective PL, and PL-excitation spectroscopies. We show that with an activation energy of $85\ifmmode\pm\else\textpm\fi{}1\mathrm{meV},$ the P-related shallow-acceptor level is the shallowest acceptor ever detected in ZnSe. The series of excited states of this acceptor reveals that it behaves like all substitutional acceptors. We thus identify it as being the simple ${\mathrm{P}}_{\mathrm{Se}}$ substitutional impurity. Its excitonic emission definitely occurs at 2.791 eV. Negligible P-related deep levels can be detected by PL. However, a line which is relatively strongly coupled to phonons is detected at 2.796 eV. This line arises from P-related defects involving P incorporated on other-than-Se-substitutional sites. Finally, the lack of conductivity of our ZnSe:P samples, which does not stem from deep defects, could be explained by an AX-like behavior of the P impurity.
23 citations
TL;DR: In this paper, the growth and characterization of p-i-n photodiodes based on ZnBeSe and ZnMgBeSe compounds was presented, and the spectral response showed a high responsivity of 0.17 A/W at 450 nm, with a rejection of ∼104 at longer wavelengths.
Abstract: We present the growth and characterization of p-i-n photodiodes based on ZnBeSe and ZnMgBeSe compounds. High-quality diodes exhibiting dark current as low as 12 nA/cm2 at −2 V bias have been fabricated. The spectral response shows a high responsivity of 0.17 A/W at 450 nm, with a rejection of ∼104 at longer wavelengths. Our results thus demonstrate the potential of ZnSe-based heterostructures for efficient detection in the visible-ultraviolet region.
22 citations
TL;DR: In this paper, the eigenfrequencies of the BeSe and ZnSe-like phonons correspond to the maxima of the dielectric model of Hon and Faust.
Abstract: Long wavelength longitudinal optical (LO) and transverse optical (TO) phonons of BeSe and ZnxBe1−xSe layers are identified in a wide composition range by using Raman spectroscopy. A two-mode behavior is clearly evidenced. As predicted by the dielectric model of Hon and Faust, the eigenfrequencies of the BeSe- and ZnSe-like LO modes correspond to the maxima of Im〈−e(ω, x)−1〉. Excellent agreement is obtained with a model where the calculations are performed by using the equations of motion and polarization derived from the modified random element isodisplacement model. Besides, the TO and LO frequencies for BeSe are determined to be 501 and 579 cm−1, respectively.
22 citations
TL;DR: In this article, a semi-transparent bilayer was used to form the Schottky contact for vertical geometry photodetectors based on n/sup -//n/sup +/-ZnSe structures grown on semi-insulating GaAs substrates by molecular beam epitaxy.
Abstract: Vertical geometry photodetectors based on n/sup -//n/sup +/-ZnSe structures grown on semi-insulating GaAs [001] substrates by molecular beam epitaxy have been realised. A semi-transparent bilayer (Ni(50 /spl Aring/)-Au (50 /spl Aring/)) was used to form the Schottky contact. The current-voltage characteristics show that the devices have an ideality factor of 1.1, a barrier height of 1.17 eV and a low dark current density of /spl sim/10/sup -8/ A/cm/sup 2/ at -4 V bias. These photodetectors have a flat responsivity above the bandgap (measured to be 0.1 A/W) and a sharp cutoff at the band edge (460 nm) of 3-4 orders of magnitude.
19 citations
TL;DR: In this paper, the authors reported on photoluminescence excitation spectroscopy performed on several (Zn, Cd)Se/ZnSe quantum wells at low temperature.
Abstract: We report on photoluminescence excitation spectroscopy performed on several (Zn, Cd)Se/ZnSe quantum wells at low temperature. Experimental results are compared with a calculation of the heavy- and light-hole excitonic transition energies. It is shown that the energy difference between the first heavy- and light-hole transitions E1H1 and E1L1 can be very sensitive to the valence-band offset under some circumstances, making a determination of this parameter then possible. The strain-free relative valence-band offset is found qv0=13%±2%. The heavy-hole excitons are type-I excitons, whereas the light-hole excitons are type-II excitons.
10 citations
TL;DR: In this paper, the authors studied the heteroepitaxial growth of Be(Zn)Se alloys on both GaAs and Si substrates using reflectivity, photoluminescence and vacuum UV ellipsometry.
9 citations
TL;DR: In this article, the defects in N-doped and undoped ZnSe layers were investigated using a low-energy positron beam to investigate the defect in GaAs:Si or znSe substrates.
Abstract: We have used a low-energy positron beam to investigate the defects in N-doped and undoped ZnSe layers grown on GaAs:Si or ZnSe substrates. In N-doped ZnSe we observe positron trapping at vacancies, identified as VSeNSe complexes, and at negative ions. Based on positron data, we give estimates for the concentrations of vacancies and negative ions. The results suggest that in addition to forming isolated NSe acceptors or VSeNSe pairs, incorporated nitrogen also forms donor-type defects leading to compensation of holes. In undoped ZnSe layers, the results show presence of Zn vacancies in concentrations 10–10 cm. The Zn vacancy concentration correlates with the dislocation density at the ZnSe/GaAs interface.
8 citations
TL;DR: In this article, the heteroepitaxial growth of ZnxBe1−xSe alloys was studied on Si, GaAs and GaP substrates and it was shown that lattice-matching is not a sufficient condition to achieve good epitaxy.
Abstract: We have studied the heteroepitaxial growth of ZnxBe1−xSe onto Si, GaAs and GaP substrates. By comparing the growth on these different substrates, we showed that lattice-matching is not a sufficient condition to achieve a good epitaxy. Then we have investigated by low-temperature photoluminescence and reflectivity spectroscopies a series of ZnxBe1−xSe alloys with Be content up to 70%. This allowed us to locate the direct-to-indirect band-gap cross over at x=0.46. We found a bowing parameter b=0.97 eV for the direct band-gap in the whole composition range. Finally, Zn0.59Be0.41Se and Zn0.55Be0.45Se alloys lattice-matched, respectively, to GaP and Si substrates are direct band-gap semiconductors which exhibit band-gap at 3.72 eV and 3.85 eV.
6 citations
TL;DR: In this paper, three types of structural defect have been observed: (i) Triangle-shaped stacking faults, with the apex close to the interface, either isolated or paired; (ii) Stacking faults generated from the surface of the ZnSe epilayer by movement of a Shockley half-loop.
Abstract: ZnSe thin films grown on GaAs(001) substrate by molecular beam epitaxy to a thickness of 2500 A have been studied by transmission electron microscopy (TEM). Three types of structural defect have been observed: (i) Triangle-shaped stacking faults, with the apex close to the interface, either isolated or paired. They are bounded by two different Shockley dislocations. (ii) Stacking faults generated from the surface of the ZnSe epilayer by movement of a Shockley half-loop. (iii) An array of perfect misfit dislocations. Their Burgers vectors are inclined to the interface. Most of them lie along 310 directions; only a few are parallel to 110.
TL;DR: In this paper, a detailed optical-spectroscopy investigation of nitrogen-doped ZnSe epitaxial layers of various doping levels and N contents which have been exposed ex situ to a hydrogen/deuterium plasma was performed.
Abstract: We report on detailed optical-spectroscopy investigations of nitrogen-doped ZnSe epitaxial layers of various doping levels and N contents which have been exposed ex situ to a hydrogen/deuterium plasma. The influence of this treatment is studied through temperature-dependent photoluminescence and selective photoluminescence. The results are similar for all samples, irrespective of their doping properties. We show that the ${\mathrm{N}}_{\mathrm{Se}}$ acceptor is strongly passivated and that the deep compensating-donor disappears after plasma exposure. In addition, the nature of the main shallow compensating-donor is changed by the $H/D$ treatment. The shallow donor in ZnSe:N which we have previously identified as a N-related defect is suppressed while the usual residual impurities of ZnSe are uncovered. Our results directly demonstrate that all compensating donors in ZnSe:N material are N-related defects, and that N may participate to nonradiative recombination centers at heavy doping. Finally, this helps selecting a few models for the deep compensating-donor and further support the implication of N interstitials in carrier compensation in ZnSe:N.
01 Mar 2000
TL;DR: In this paper, the authors reviewed the current status of research on ZnSe-based heterostructures for bluegreen laser diodes, focusing on a few selected critical issues.
Abstract: We review the current status of research activity on ZnSe-based heterostructures for bluegreen laser diodes (LDs), focusing on a few selected critical issues. Early investigations on defect microstructures allowed to strongly enhance the lifetime of LDs. However, the LD lifetime seems to saturate now, and we point out that the model proposed for explaining the degradation of LD does not predict such a saturation. Next, we detail the mechanisms responsible for carrier compensation in p-type ZnSe and we survey the properties of ZnMgSSe and ZnMgBeSe wide bandgap quaternary alloys which are used as cladding layers in LDs. We emphasize that the low p-type dopability of ZnSe and related materials has a dramatic impact on the performance of LDs in terms of emitted wavelength as well as device lifetime.
TL;DR: ZnSe:N samples with different doping levels have been exposed ex situ to hydrogen (H) or deuterium (D) plasma and secondary ion mass spectroscopy reveals that the H/D profile matches exactly the N profile in all samples, whatever the plasma-exposure conditions.
TL;DR: In this paper, the vertical geometry transparent-Schottky-barrier photodetectors based on ZnSe and ZnMgBeSe structures grown on GaAs substrates are presented.
Abstract: We report on the fabrication and characterization of vertical-geometry transparent-Schottky-barrier photodetectors based on ZnSe and ZnMgBeSe structures grown on GaAs substrates. These detectors operate in the blue and ultraviolet spectral range. A responsivity as high as 0.12 A/W has been obtained at 460 nm with a sharp cutoff and a rejection rate of 5 × 103. A linear variation of the photocurrent versus the incident optical power has been measured which proves the absence of an internal gain mechanism. Wavelength cutoffs can be tuned from 460 to 415 nm by increasing Mg and Be contents. Very low dark current levels have been obtained thanks to the growth of ZnMgBeSe structures lattice matched onto GaAs substrates.