Characterization of Interface States in ZnO Varistors using Isothermal Capacitance Transient Spectroscopy

Isothermal capacitance transient spectroscopy measurements were performed to study the reoxidizing induced change in interface states in (Sr, Ca)TiO3−x based ceramics. A discrete acceptor type trap level was detected with reoxidation below the oxidation temperature of grain surfaces, but two deep levels were detected with reoxidation above this temperature. These ICTS results are in good agreement with the previous report with the DLTS measurements. These interface states are considered to originate from chemisorbed oxygen (O2−, O−) on grain surfaces. The O− and O2− chemisorption levels contribute to the non-ohmic conduction with reoxidizing anneals below and above the oxidation temperature, respectively.

Download Full-text

Quantitative Icts Measurement of Interface States at Grain Boundaries in ZnO Varistors

MRS Proceedings ◽

10.1557/proc-500-213 ◽

1997 ◽

Vol 500 ◽

Author(s):

K. Mukae ◽

A. Tanaka

Keyword(s):

Grain Boundaries ◽

Interface States ◽

Zno Varistors ◽

Single Grain ◽

Doped Zno ◽

Transient Spectroscopy ◽

Er Doped ◽

Capacitance Transient ◽

Rare Earth Doped ◽

Density Of Interface States

ABSTRACTIsothermal capacitance transient spectroscopy(ICTS) measurement is applied to ZnO:Pr varistors. A simple peak corresponding to the interface states at grain boundaries was obtained and the energy level of the interface states revealed to be monoenergetic and located around 0.9eV below the conduction band. The cross section was calculated as around 10−14 cm2. Quantitative treatment of the ICTS intensity in relation to the density of interface states at grain boundaries was established. The density of interface states was obtained from the linear relation between ICTS intensity and reciprocal carrier density(ND). According to experiments on series of rare-earth doped ZnO varistors, the interface states of Pr, Tb or Nd doped ZnO varistors had higher density of states than La or Er doped varistors. Moreover, application of ICTS measurement to single grain boundary using microelectrodes revealed that higher density of interface states gave higher nonlinearity in I-V characteristics.

Download Full-text

Characterization of Ti2+/Ti3+ donor level in ZnSe by isothermal capacitance transient spectroscopy

Applied Physics Letters ◽

10.1063/1.118623 ◽

1997 ◽

Vol 70 (12) ◽

pp. 1587-1589 ◽

Cited By ~ 1

Author(s):

H. Okada

Keyword(s):

Donor Level ◽

Transient Spectroscopy ◽

Capacitance Transient ◽

Isothermal Capacitance Transient Spectroscopy

Download Full-text

Transient Capacitance Characterization of Deep Levels in Undoped and Si-Doped GaN

MRS Proceedings ◽

10.1557/proc-764-c3.39 ◽

2003 ◽

Vol 764 ◽

Author(s):

S. Nakamura ◽

P. Liu ◽

M. Suhara ◽

T. Okumura

Keyword(s):

Chemical Vapor ◽

Deep Levels ◽

Yellow Luminescence ◽

Capacitance Measurements ◽

Transient Capacitance ◽

Si Doped ◽

Transient Spectroscopy ◽

Capacitance Transient ◽

Isothermal Capacitance Transient Spectroscopy

AbstractThe deep levels in both undoped and Si-doped GaN layer grown by metalorganic chemical vapor deposition have been characterized by photocapacitance and transient capacitance spectroscopy. The increase in the photocapacitance was observed in both GaN samples in the range of 1.8 to 2.2 eV. This is due to the photoionization of carriers from the deep levels associated with the yellow luminescence (YL). In addition, the transient capacitance measurements after the photoionization were also performed in the range of 1.8 to 3.4 eV. The notable transient of capacitance was observed at the photon energies of about 2.1 and 3.4 eV, the former could be associated with the change in the charge state of the YL center and latter might stem from some other defects capturing photogenerated carriers. By using the isothermal capacitance transient spectroscopy (ICTS) analysis, the ICTS peaks due to the deep levels associated with YL were detected at about t = 150 s in both GaN samples. In addition, another ICTS peak was detected only in the Si-doped GaN samples. It is considered that this peak is associated with the deep levels deeper than YL levels and the deeper levels originate from defects induced by Si doping.

Download Full-text