Deep-Level Optical Spectroscopy Investigation of Band Gap States in AlGaN/GaN Hetero-Interfaces

2008 ◽  
Vol 1 ◽  
pp. 091101 ◽  
Author(s):  
Yoshitaka Nakano ◽  
Yoshihiro Irokawa ◽  
Masaki Takeguchi
Keyword(s):  
Band Gap ◽  
Optical Spectroscopy ◽  
Deep Level ◽  
Gap States

Band Gap States in AlGaN/GaN Hetero-Interface Studied by Deep-Level Optical Spectroscopy

2009 ◽  
Vol 1202 ◽  
Author(s):  
Yoshitaka Nakano ◽  
Keiji Nakamura ◽  
Yoshihiro Irokawa ◽  
Masaki Takeguchi
Keyword(s):  
Steady State ◽  
Optical Spectroscopy ◽  
Deep Level ◽  
Electron Gas ◽  
Two Dimensional ◽  
Dimensional Electron ◽  
Two Dimensional Electron Gas ◽  
Capacitance Voltage ◽  
Dimensional Electron Gas ◽  
Gap States

AbstractPlanar Pt/AlGaN/GaN Schottky barrier diodes (SBDs) have been characterized by capacitance-voltage and capacitance deep-level optical spectroscopy measurements, compared to reference Pt/GaN:Si SBDs. Two specific deep levels are found to be located at ∼1.70 and ∼2.08 eV below the conduction band, which are clearly different from deep-level defects (Ec - 1.40, Ec - 2.64, and Ec - 2.90 eV) observed in the Pt/GaN:Si SBDs. From the diode bias dependence of the steady-state photocapacitance, these levels are believed to stem from a two-dimensional electron gas (2DEG) region at the AlGaN/GaN hetero-interface. In particular, the 1.70 eV level is likely to act as an efficient generation-recombination center of 2DEG carriers.

Intrinsic Degradation in Alq3-Based OLEDs Probed by Deep-Level Optical Spectroscopy

2009 ◽  
Vol 1212 ◽  
Author(s):  
Yoshitaka Nakano
Keyword(s):  
Optical Spectroscopy ◽  
Deep Level ◽  
Single Layer ◽  
Molecular Structures ◽  
Near Band Edge ◽  
Electronic Band ◽  
Emissive Region ◽  
Electronic Band Gap ◽  
Gap States ◽  
Intrinsic Degradation

AbstractWe have successfully investigated degradation-induced variations in electronic band-gap states in the emissive region of the Alq3-based OLEDs by a deep-level optical spectroscopy technique. Through the intrinsic degradation, both deep-level traps and near-band-edge transitions in the Alq3 emissive zone are found to be red-shifted significantly towards their corresponding bulk levels of the Alq3 single layer. These variations in the interfacial electronic states are probably induced by the intrinsic degradation and indicate that initial molecular structures characteristic of the Alq3 emissive zone are transformed into the bulk-like relaxed ones through the degradation.

Lattice and electronic effects in rutile TiO2 containing charged oxygen defects from ab initio calculations

2009 ◽  
Vol 1160 ◽  
Author(s):  
Seong-Geon Park ◽  
Blanka Magyari-Köpe ◽  
Yoshio Nishi
Keyword(s):  
Oxygen Vacancy ◽  
Band Gap ◽  
Conduction Band ◽  
Density Functional ◽  
Deep Level ◽  
Vacancy Defect ◽  
Conduction Band Minimum ◽  
Electronic Effects ◽  
Atomic Relaxation ◽  
Gap States

AbstractWe performed first-principle simulation for the study of oxygen vacancy defect in rutile TiO2 based on density functional theory. The effects of a vacancy on the electronic structure of rutile TiO2 were studied. Here we have employed neutral and charged oxygen vacancy in the supercell to address the resistance switching mechanism. Neutral vacancy induces the band gap states at deep level, ∼0.7 eV below the conduction band minimum, which is occupied by highly localized electrons. The calculation results of positively charged oxygen vacancy show that larger atomic relaxation surrounding oxygen vacancy results in the stretching of Ti-O bond around vacancy, thus band gap states are formed near the conduction band minimum.

Europium Induced Deep Levels in Hexagonal Silicon Carbide

2006 ◽  
Vol 527-529 ◽  
pp. 659-662
Author(s):  
G. Pasold ◽  
F. Albrecht ◽  
C. Hülsen ◽  
R. Sielemann ◽  
W. Witthuhn
Keyword(s):  
Silicon Carbide ◽  
Band Gap ◽  
Deep Level ◽  
Energy Transfer Process ◽  
Energy Levels ◽  
Radioactive Tracer ◽  
Chemical Identification ◽  
Concentration Sensitivity ◽  
Transient Spectroscopy ◽  
Gap States

Silicon carbide (SiC) was investigated for deep band gap states of europium by means of deep level transient spectroscopy (DLTS). The knowledge of the properties of optoelectrically active impurities or defects is essential for a detailed understanding of the energy-transfer process resulting in the observable excitations [1]. SiC-samples of the polytypes 4H as well as 6H are ion-implanted by different europium- isotopes in order to obtain a chemical identification of the characterized energy levels. Here the concentration sensitivity of the DLTS is applied to observe the elemental transmutation of the incorporated radioactive tracer atoms 146Eu (t1/2=4.51 d) and 147Eu (t1/2=24.6 d). DLTS on samples implanted with stable Eu-ions (153Eu) was carried out for comparison and manifestation of the results. From these studies 5 Eu-related deep band gap levels are established: in 4H-SiC two levels at EV+0.86(2) eV and EC−0.47(2) eV, and in 6H-SiC three levels at EV+0.88(2) eV, EC−0.29(2) eV and EC−0.67(2) eV.

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