Toshiyuki Ido

Detection of traps in ZnSe grown by liquid phase epitaxy

Abstract The traps in ZnSe epitaxial layers grown on (111) ZnSe substrates were investigated by photocapacitance and deep level transient spectroscopy (DLTS) methods. The photocapacitance study showed a donor trap at 0.14 eV and two acceptor traps at 0.57 and 0.10 eV, which were identified as a self-activated center and a Na or Li acceptor, respectively. The DLTS study elucidated a 0.32 eV trap in a P-doped sample and a 0.30 eV trap in an undoped sample, which seems to be due to a Se vacancy. Traps were found also at 0.15, 0.29 and 0.52 eV in a Ga-doped sample. The DLTS spectra of the first two traps changed markedly under the light irradiation.

Deep-Level Transient Spectroscopy of Nitrogen-Doped ZnSe Grown by Metalorganic Vapor Phase Epitaxy

N-doped ZnSe, which was grown on (001)GaAs substrate by metalorganic vapor phase epitaxy (MOVPE) using NH3, was characterized by deep-level transient spectroscopy (DLTS) and photoluminescence (PL). We observed three major deep hole traps of which the energy levels are 640±30 meV, 490±30 meV, 400±20 meV. The density of these traps depends on NH3 supply rate or the ratio of the molar supply rate of Se to Zn.

Photoacoustic spectra of Sb-doped ZnSe

Photoacoustic (PA) spectra were made on Sb-doped ZnSe samples grown by metalorganic vapor phase epitaxy (MOVPE). The samples deposited at a low temperature under irradiation show the PA spectrum with a sharp edge near the band gap and with three distinct peaks. From the Sb flow rate dependence of PA peaks, two of them seem to be related to Sb impurities. Non-doped sample shows only one peak, which is tentatively ascribed to the deep level associated with Se defects.

Metalorganic Vapor Phase Epitaxy of Sb-Doped ZnSe

The Sb-doped ZnSe was grown on (100)GaAs substrate by using the Metalorganic Vapor Phase Epitaxy method in atmospheric pressure in order to obtain a p-type ZnSe film. The C-V measurement of the Sb-doped ZnSe layer suggests a p-type conduction. The maximum space charge concentration obtained was 1.5×1016 cm-3. The acceptor level of Sb, which was estimated from the photoluminescence spectrum, was found to be 69 meV.

Diffusion Length of Holes in n-ZnSe Measured by Schottky Barrier Photovoltage Method

The diffusion length (L ) of holes in undoped n-type ZnSe has been measured by using the Schottky barrier photovoltage method. The samples measured were single crystals and epitaxial layers which were prepared by metalorganic chemical vapor deposition. The values of L were 1 µm for single crystals and 0.15 µm for epilayers. The lifetimes estimated from those values were 4.5 ns and 0.10 ns, respectively.

Antimony Treatment Effect on Cd1-xMnxTe Growth on GaAs by Metal-Organic Vapor Phase Epitaxy

A heteroepitaxial film of Cd1-xMnxTe has been grown on a (100)GaAs substrate by metal-organic vapor phase epitaxy. It is shown that a high quality Cd1-xMnxTe film can be grown on the GaAs substrate by pretreating the GaAs substrate with triethyl antimony at 650°C. The best full width at half maximum of the X-ray diffraction peak of the Cd1-xMnxTe film (x=0.12) obtained was 650 arc sec. The effects of the triethyl antimony on the film quality of Cd1-xMnxTe are discussed.

Deep levels in Sb-doped ZnSe fabricated by metalorganic vapor-phase epitaxy

Abstract Sb-doped ZnSe samples were deposited on the (001)GaAs substrate by metalorganic vapor-phase epitaxy (MOVPE). Isothermal capacitance transient spectroscopy (ICTS) and spectral analysis of deep-level transient spectroscopy (SADLTS) were used to characterize deep levels of Sb-doped ZnSe. The p-type sample grown by MOVPE at 490°C in the darkness shows three ICTS peaks. Three deep levels were observed in the N-doped ZnSe deposited by MOVPE. Using the SADLTS, we can estimate the activation energy and the capture-cross section distributions of that hole traps. We also examined samples that were photoassist-deposited at lower temperature. The non-doped ZnSe thin films were also measured to check the effects of light irradiation during the deposition. We could get only n-type samples and the light irradiation generates the new level of the electron traps. Sb doping generates other new levels. The levels that correspond to trap E1 in the light-irradiated Sb-doped samples are constructed from two adjacent levels in SADLTS, and one new level near trap E1 can be observed in SADLTS.

Deep hole trap level of nitrogen-doped ZnSe grown by metalorganic vapor phase epitaxy

Abstract We investigated the hole trap level of nitrogen-doped ZnSe grown by a metalorganic vapor phase epitaxy method. The deep level transient spectroscopy (DLTS) signal and the C - V profile were measured to obtain the trap level, the capture cross section and the trap concentration. A deep hole trap level of about 1 eV from a valence band (labeled TLIS) was extracted from the tail of the DLTS peak. The distributions of the capture cross section and the trap level of the samples for different growth conditions were drawn in a figure to investigate the validity of the resolution of the DLTS signal. The origin of TLIS is thought to be in relation to the ionized acceptor or the charged acceptor-like localized defects.

Growth and Characterization of Vanadium-Doped ZnSe by Metalorganic Vapor Phase Epitaxy

Vanadium-doped ZnSe was epitaxially grown on a (100) GaAs substrate by metalorganic vapor phase epitaxy under atmospheric pressure. The effects of the molar supply ratio of dimethylzinc to dimethylselenide on crystallinity were investigated to determine the optimum vanadium doping conditions. In the present study, as dopant sources of vanadium, vanadocene and triethoxyvanadyl were used. When triethoxyvanadyl was used as a dopant source, the crystal growth condition of vanadium-doped ZnSe changed from epitaxial growth to polycrystal growth at a molar supply ratio between 1.2 and 1.5. The magnetic property of vanadium-doped ZnSe fabricated at a molar supply ratio of 1.2 was measured using a superconducting quantum interface device at room temperature.

Crystal growth of vanadium-doped ZnSe using triethoxyvanadyl by metal-organic vapor phase epitaxy

As a new diluted magnetic semiconductor, vanadium-doped ZnSe is theoretically predicted to induce ferromagnetism above room temperature without carrier doping. Vanadium-doped ZnSe was epitaxially grown on (100) GaAs substrate by metal-organic vapor phase epitaxial method in an atmospheric pressure. As a dopant source of vanadium, triethoxyvanadyl was used. The influences of molar supply ratio of dimethylzinc to dimethylselenide on crystallinity were investigated in order to research the optimum vanadium-doping condition. The crystal growth condition of vanadium-doped ZnSe changed from epitaxial growth to polycrystal growth at molar supply ratio between 1.2 and 1.5.