S. Y. Wang

Compensation processes in nitrogen doped ZnSe

We have examined the compensation processes in nitrogen doped ZnSe grown by molecular beam epitaxy. Two independent donor–acceptor pair emission processes have been observed in photoassisted grown layers and detailed temperature dependence measurements have allowed us to conclude that a deep compensation donor with a binding energy of 44 meV exists in more heavily doped material. We propose that the compensating donor is a complex involving a native defect such as the (VSe‐Zn‐NSe) single donor and this suggestion is supported by the observation of changes in the carrier concentration profile with time.

ZnSe‐ZnCdSe quantum confined Stark effect modulators

We report room temperature operation of a II‐VI p‐i‐n quantum confined Stark effect modulator using a ZnSe‐Zn0.8Cd0.2Se multiple quantum well structure within a ZdSe p‐n junction. A n‐type ZnSe layer was used as a novel contact to the p‐type ZnSe. Results are given for photovoltage spectroscopy, absorption, and differential absorption as a function of the applied electric field.

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.

Blue stimulated emission from a ZnSe p‐n diode at low temperature

Laser diode structures have been fabricated using molecular beam epitaxy with iodine from an electrochemical source for the n‐type doping and nitrogen from a plasma source for the p‐type doping. CV profiling using electrochemical etching shows uniform p doping of 4×1017 cm−3 and n doping of 1×1018 cm−3. Under pulsed current excitation blue emission at 470 nm is observed at room temperature which increases in intensity at liquid helium temperatures. Above a current density threshold of 50 A cm−2 stimulated emission is observed between 448–473 nm with a complicated mode structure.

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.

Electrochemical capacitance‐voltage profiling of n‐type molecular beam epitaxy ZnSe layers

We report the use of electrochemical capacitance‐voltage profiling of n‐type ZnSe layers by the use of NaOH electrolyte. Samples with both uniform and staircase doping profiles have been measured with concentrations ranging over 1016–1019 cm−3. The profiling technique has revealed in some samples regions of lower carrier concentration at the surface and at the ZnSe/GaAs interface. Our results demonstrate that this powerful technique can now be used for assessing the growth parameters of wideband gap II‐VI materials in the same way that is widely accepted for III‐V semiconductors.

UV laser assisted growth of molecular beam epitaxial ZnSe

Abstract Photo-assisted molecular beam epitaxy of ZnSe on GaAs substrates with UV irradiation is reported. The growth rate is observed to be a function of the layer thickness and at high UV levels growth can be totally supressed. Photo-assisted doping has been investigated for the first time in ZnSe and changes of up to 20x in the doping level are reported for iodine, n-type doped material. The results are discussed in terms of hole accumulation at the surface affecting the incorporation of selenium and iodine.

Electrical characterization of iodine doped molecular beam epitaxial ZnSe

We report the use of an electrochemical iodine cell to dope epitaxial ZnSe grown by molecular beam epitaxy (MBE) over a range of carrier concentrations from 1016 to 1019 cm-3. The doping levels throughout the layers have been measured by electrochemical CV profiling and calibrated in terms of the cell flux. Photoluminescence and Hall data confirm the growth of well behaved n-type ZnSe.

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 ue5f8Znue5f8N Se for the deep acceptor and N Se ue5f8N Zn for the deep donor.

Compensation processes in molecular beam epitaxially grown zinc selenide doped with nitrogen

Abstract Recent work has shown that nitrogen produced in a plasma source is a p-type dopant in MBE grown ZnSe with N a − N d to 1×10 18 cm -3 , but at these concentrations the material is highly compensated. In a previous study, we have examined the PL spectra of nitrogen doped material grown in our laboratory and have shown that there are two sets of donor-acceptor pair (DAP) peaks which can be explained by a simple model involving a nitrogen acceptor and two donors. The first donor is a native shallow donor and the second is a nitrogen related compensating donor thought to be a complex of the form V Se -Zn-N Se . Optically detected magnetic resonance results on samples showing both shallow and deep DAP luminescence show signals due to the shallow isotropic donors and deep anisotropic donors consistent with our proposed model. Calculations of the vacancy concentrations and degree of compensation that should be expected in nitrogen doped ZnSe show that at all temperatures and under all growth conditions the material is highly undersaturated with vacancies. The barriers operating to prevent the compensation are discussed.