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We study the growth and optical properties of Cr-doped CdTe/ZnTe nanostructures grown on ZnTe (001) substrates by molecular beam epitaxy. In-situ reflection high-energy electron diffraction is used to study the growth processes and strain relaxation behaviors of Cr-doped CdTe quantum dots (QDs). After 4.5�ML deposition, the surface lattice parameter begins to increase remarkably, which indicates that the two-dimensional growth mode is terminated and the CdTe layer grows in a three-dimensional mode. Low temperature photoluminescence spectra of Cr-doped CdTe QDs (Tcr = 900 °C) show a broad emision. With increasing the Cr cell temperature above 1000 °C, the luminescence from CdTe QDs disappears and the broad luminescence at around 1.6 eV becomes dominant.

Objective To determine the long-term efficacy and complications of sacral nerve stimulation as an alternative therapy for functional unobstructive urinary retention, often considered to be psychogenic and effectively treated by clean intermittent catheterization, but for which pelvic floor dysfunction has been recognized as a possible cause. Patients and methods Twenty patients (17 women and three men, mean age 48 years) with idiopathic, unobstructive functional urinary retention and in whom other forms of therapy had failed, had a pulse generator implanted (Medtronic, Minneapolis, MN, USA) and a sacral nerve implant. Their mean duration of symptoms was 68 months; 13 patients had chronic pelvic and perineal pain associated with their obstructive voiding symptoms. All patients were managed with clean intermittent catheterization and pharmacological therapy (α-blockers) before the procedure. All patients had a percutaneous nerve evaluation before the permanent implant, which showed> 50% improvement in their symptoms. All patients were evaluated at 1, 6 12, 18 and 24 months, then yearly thereafter. The results were assessed both subjectively by patient's symptoms and objectively by checking the postvoid residual volume (PVR) and voided volume. Results Eighteen patients were able to void spontaneously with a mean increase in voided volume from 48 to 198 mL, and a significant decrease in PVR from 315 to 60 mL. Eighteen of the patients had a ≥ 50% improvement in their symptoms and said they would recommend the therapy to a friend or relative. Complications occurred in six patients. Conclusion Sacral nerve stimulation is an effective and durable new approach to functional urinary retention, with few associated complications. Test stimulation provides a valuable tool for selecting patients.

We have investigated the effects of band filling and thermal escape on the temperature dependence and excitation power dependence of photoluminescence of CdTe QDs grown by molecular beam epitaxy on ZnTe(100) substrate. The absorption spectrum indicates that the PL spectrum consists of two peaks. The experimental results of excitation power dependence were well simulated by the rate equation model taking into account the effect of band filling. The temperature dependence of PL showed significant difference for different excitation powers. It is suggested that either the wetting layer or excited states play an important role in band filling and thermal escape.

We have investigated the ZnTe-based material system for the application to light-emitting devices. To this end, ZnTe homoepitaxy techniques have been developed to grow high-quality epitaxial layers. The conductivity control of ZnTe and ZnMgSeTe layers have been investigated. High structural quality n-type ZnTe layers with high carrier concentration are achieved by aluminum doping. Ambipolar conductivity control of quaternary layers is achieved. Aluminum doped ZnMgSeTe layers show a net carrier concentration of 5 × 10 16 cm -3 , while a high hole concentration of 2.5 x 10 19 cm -3 is achieved by p-type doping using a nitrogen plasma source. Based on those results, Zn 1-x Cd x Te/ZnMgSeTe triple-quantum-well(TQW) LED structures were fabricated. Bright electroluminescence was obtained at room temperature at the wavelength of 604 nm from Zn 0.7 Cd 0.3 Te and at 566 nm from Zn 0.85 Cd 0.15 Te TQW-LED.

Molecular beam epitaxy of Al doped n-type ZnSe is studied. Growth conditions such as Al cell temperature and substrate temperature are systematically examined. The electrical, optical and structural properties of ZnSe : Al layers are investigated. ZnSe : Al layers show high electron concentration of 8.37 × 10 18 cm -3 with low electrical conductivity of 6.92 x 10 -3 Ω cm along with high crystallinity.

The linear electro-optic (LEO) or Pockels coefficient above the fundamental edge E 0 of ZnTe has not been determined yet as far as we know. In this work, we have measured the LEO coefficient of ZnTe in the absorbing region by reflectance difference or reflectance anisotropy spectroscopy (RDS or RAS), and we have obtained two remarkable peaks near the E, and E 1 + Δ 1 critical points.

We have fabricated ZnCdSe/ZnMgBeSe single quantum well (SQW) light emitting diode (LED) structures with ZnSe:N/BeTe:N p-contact layers. The electrical properties of this p-contact layer scheme were evaluated for the use in ZnSe-based II–VI LDs. The specific contact resistance for Au/p-ZnSe/p-BeTe ohmic contact layers, which was measured by the transmission line model (TLM) method, was as low as 4.2 × 10–4 Ωcm2 even without annealing when the ZnSe layer thickness is 5 nm. The composition of quaternary ZnMgBeSe was determined using a ZnBeSe/ZnMgBeSe layer structure by PL and X-ray measurements. The p-type doping property was investigated for ZnMgBeSe with different compositions, and Na–Nd drastically decreases with increasing band gap energy the same as that of the ZnMgSSe:N system. The fabricated LEDs show a strong electroluminescence under dc bias at room temperature.