P.J. Thompson

Compensating acceptors and donors in nitrogen δ-doped ZnSe layers studied by photoluminescence and photoluminescence excitation spectroscopy

The compensating acceptors and donors in nitrogen δ‐doped ZnSe epilayers grown by molecular beam epitaxy using a nitrogen rf‐plasma source are studied by means of photoluminescence (PL) and photoluminescence excitation spectroscopy (PLE). The temperature dependence of PL and PLE spectra obtained from the nitrogen δ‐doped layers is investigated in detail, and a deep acceptor and a deep donor with ionization energies of ∼170 and ∼88 meV are reported for the nitrogen δ‐doped layers. These two deep centers are assigned to N clusters, i.e., NSe‐Zn‐NSe for the deep acceptor and NSe‐NZn for the deep donor.

A compensating donor with a binding energy of 57 meV in nitrogen‐doped ZnSe

A compensating deep donor with a binding energy of 57 meV in ZnSe:N epilayers has been studied by means of photoluminescence and selectively excited photoluminescence (SPL) spectroscopy. The emission of 2.766 eV due to transitions between the deep donors and free holes (DdF) was observed at 4 K under strong excitation conditions. The emission at 2.681 eV due to transitions between deep donors and nitrogen acceptors (DdAP) is attributed to the same deep donor as that of the DdF emission through a detailed SPL study. It is also demonstrated that the SPL technique is important for studying the deep levels in ZnSe:N.

Room temperature ZnSe/ZnCdSe bistable self‐electro‐optic effect device operating at 488 nm

Optical bistability at room temperature has been observed for the first time in a II‐VI semiconductor self‐electro‐optic effect device fabricated by molecular beam epitaxy. The optical switch is based on a ZnSe/ZnCdSe multiple quantum well structure situated within a p‐n junction and the devices operate at 488 nm in the blue‐green spectral region.

Compensating processes in nitrogen δ-doped ZnSe layers studied by photoluminescence and photoluminescence excitation spectroscopy

Abstract The compensating acceptors and donors in nitrogen δ-doped ZnSe epilayers grown by molecular beam epitaxy using a nitrogen rf-plasma source are studied by means of photoluminescence and photoluminescence excitation spectroscopy. A deep acceptor and a deep donor with ionization energies of ∼ 170 and ∼ 88 meV are reported for the nitrogen δ-doped layers. These two deep centres are assigned to N-clusters, i.e., N Se ZnN Se for the deep acceptor and N Se N Zn for the deep donor.

Piezoelectric effect in ZnSe/ZnCdSe quantum wells grown on (211)B GaAs

The piezoelectric effect has been demonstrated for the first time in strained ZnSe/ZnCdSe quantum wells grown on (211)B GaAs substrates. A piezoelectric field strength of 1.1 X10 5 V/cm has been observed in Zn 0.8 Cd 0.2 Se quantum wells that have a 1.3% lattice mismatch with the substrate.

A ZnSe/ZnCdSe quantum well symmetric self-electro-optic effect device operating in the blue-green region

Abstract In this paper, we report the first observation of a II–VI symmetric self-electro-optic device (SEED) operating as an optical switch at a wavelength of 488 nm at room temperature. Quantum confined Stark effect modulators based on ZnSe/ZnCdSe p-i-n structures were fabricated by molecular beam epitaxy and used in the symmetric mode where one modulator was used to bias a second modulator which showed bistable transmission characteristics with a contrast ratio of 1.5:1 between the high and low transmission states.

Photoluminescence excitation spectroscopic studies of nitrogen doped ZnSe

Photoluminescence excitation spectroscopy (PLE) of nitrogen doped ZnSe epilayers is reported here for the first time. The dependence of the PLE spectra on the net acceptor concentration in ZnSe:N and the temperature has been investigated. A new radiative transition at 2.732 eV is revealed in highly doped ZnSe:N, and is attributed to a transition between the valence band and a new donor level with an ionisation energy of 88 meV. The effect of strain on the exciton spectra in undoped and N-doped layers is discussed.

Nitrogen doping during atomic layer epitaxial growth of ZnSe

This letter reports the growth and characterization of ZnSe:N layers by atomic layer epitaxy (ALE) using a nitrogen rf‐plasma source. The ALE‐grown ZnSe:N layers have been investigated in terms of in situ reflection high electron energy diffraction and ex situ capacitance–voltage profiling and photoluminescence spectroscopy. The net acceptor concentration in the ALE‐grown layer has been obtained as high as 1.2×1018 cm−3 and the ALE layers of ZnSe:N show reduced number of compensating deep centers compared with the ZnSe:N grown by molecular beam epitaxy. The effects of the Fermi level at a growing surface on the generation of compensating donors with a binding energy of 57 meV are also discussed.

Compensation in p-type ZnSe based semiconductors

Abstract Over the past few years nitrogen has been shown to be by far the best dopant to use in the production of p-type ZnSe, although it is often highly compensated. This review describes the evidence for compensation in ZnSe:N due to the presence of selenium vacancy complexes and also more recent evidence for the presence of other compensating donors and deep acceptors. The use of hydrogen plasma exposure to reduce the concentrations of these complex species is discussed. Various models have previously been presented to explain the compensation of ZnSe, and here we discuss the role of surface states in the pinning of the Fermi level and its effect on compensation. Finally, we show that the compensating selenium vacancies have been found by many authors to be mobile and discuss the mechanisms which may account for this behaviour.

II-VI quantum confined Stark effect waveguide modulators

Quantum confined Stark effect p‐i‐n waveguide modulators, grown on GaAs substrates by molecular beam epitaxy and using an undoped ZnSe/ZnCdSe multiquantum well structure as the guiding layer, have exhibited intensity modulation at wavelengths of 496 and 501 nm with extinction ratios of 6 and 4, respectively. These same devices have also demonstrated a transverse linear electro‐optic effect observed as a superimposed secondary effect on the lateral intensity modulation at 514 nm in the form of phase modulation in the output of the same device. Intensity modulation has also been observed in quaternary laser waveguide structures, indicating that this is a device structure which is suitable for monolithic integration.