scholarly journals Interface Effects on the Persistent Photoconductivity in Thin GaN and AlGaN Films

1999 ◽  
Vol 4 (S1) ◽  
pp. 520-525 ◽  
Author(s):  
O. P. Seifert ◽  
O. Kirfel ◽  
M. Munzel ◽  
M. T. Hirsch ◽  
J. Parisi ◽  
...  
Keyword(s):  
Interface Properties ◽  
Persistent Photoconductivity ◽  
Temperature Dependent ◽  
Substrate Side ◽  
Electrical Effect ◽  
Order Of Magnitude ◽  
Hall Effect Measurements ◽  
Film Substrate ◽  
Gan Film ◽  
Interface Effects

Thin films of GaN and its alloy AlGaN are investigated with respect to their properties of the persistent photoconductivity (PPC). In this work, we show that the film-substrate interface plays an important role for the metastable electrical effect. Strongly absorbed bandgap light causes an increase of photoconductivity which is about one order of magnitude higher when the sample is illuminated from the substrate side near the interface than from the growth side. To access the interface properties at the substrate, we use temperature-dependent Hall effect measurements. The smallest PPC effect was observed for the GaN film with the best interface properties grown on SiC.

Interface Effects on the Persistent Photoconductivity in Thin GaN and AlGaN Films

1998 ◽  
Vol 537 ◽  
Author(s):  
O. P. Seifert ◽  
O. Kirfel ◽  
M. Munzel ◽  
M. T. Hirsch ◽  
J. Parisi ◽  
...  
Keyword(s):  
Interface Properties ◽  
Persistent Photoconductivity ◽  
Temperature Dependent ◽  
Substrate Side ◽  
Electrical Effect ◽  
Order Of Magnitude ◽  
Hall Effect Measurements ◽  
Film Substrate ◽  
Gan Film ◽  
Interface Effects

AbstractThin films of GaN and its alloy AlGaN are investigated with respect to their properties of the persistent photoconductivity (PPC). In this work, we show that the film-substrate interface plays an important role for the metastable electrical effect. Strongly absorbed bandgap light causes an increase of photoconductivity which is about one order of magnitude higher when the sample is illuminated from the substrate side near the interface than from the growth side. To access the interface properties at the substrate, we use temperature-dependent Hall effect measurements. The smallest PPC effect was observed for the GaN film with the best interface properties grown on SiC.

scholarly journals Growth of (110) GaAs/GaAs by Molecular Beam Epitaxy

1985 ◽  
Vol 46 ◽  
Author(s):  
L.T. Parechanian ◽  
E.R. Weber ◽  
T.L. Hierl
Keyword(s):  
Molecular Beam Epitaxy ◽  
Substrate Temperature ◽  
Hall Effect ◽  
Room Temperature ◽  
Molecular Beam ◽  
Defect Density ◽  
Temperature Dependent ◽  
Mbe Growth ◽  
Order Of Magnitude ◽  
Hall Effect Measurements

AbstractThe simultaneous molecular beam epitaxy (MBE) growth of (100) and (110) GaAs/GaAsintentionally doped with Si(∼lE16/cm^3) was studied as a function of substrate temperature, arsenic overpressure, and epitaxial growth rate. The films wereanalyzed by scanning electron and optical microscopy, liquid helium photoluminescence (PL), and electronic characterization.For the (110) epitaxal layers, an increase in morphological defect density and degradation of PL signal was observed with a lowering of the substrate temperature from 570C. Capacitance-voltage (CV) and Hall Effect measurements yield room temperature donor concentrations for the (100) films of n∼l5/cm^3 while the (110) layers exhibit electron concentrations of n∼2El7/cm^3. Hall measurements at 77K on the (100) films show the expected mobility enhancement of Si donors, whereas the (110) epi layers become insulating or greatly compensated. This behavior suggests that room temperature conduction in the (110) films is due to a deeper donor partially compensated by an acceptor level whose concentration is of the same order of magnitude as that of any electrically active Si. Temperature dependent Hall effect indicates that the activation energy of the deeper donor level lies ∼290 meV from the conduction band. PL and Hall effect indicate that the better quality (110) material is grown by increasingthe arsenic flux during MBE growth. The nature of the defects involved with the growth process will be discussed.

Results of SIMS, LTPL and Temperature-Dependent Hall Effect Measurements Performed on Al-Doped α-SiC Substrates Grown by the M-PVT Method

2006 ◽  
Vol 527-529 ◽  
pp. 633-636 ◽  
Author(s):  
Sylvie Contreras ◽  
Marcin Zielinski ◽  
Leszek Konczewicz ◽  
Caroline Blanc ◽  
Sandrine Juillaguet ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Hall Effect ◽  
Vapor Transport ◽  
Physical Vapor Transport ◽  
Temperature Dependent ◽  
Large N ◽  
Hall Effect Measurements ◽  
Van Der Pauw ◽  
P Type ◽  
Made In

We report on investigation of p-type doped, SiC wafers grown by the Modified- Physical Vapor Transport (M-PVT) method. SIMS measurements give Al concentrations in the range 1018 to 1020 cm-3, with weak Ti concentration but large N compensation. To measure the wafers’ resistivity, carrier concentration and mobility, temperature-dependant Hall effect measurements have been made in the range 100-850 K using the Van der Pauw method. The temperature dependence of the mobility suggests higher Al concentration, and higher compensation, than estimated from SIMS. Additional LTPL measurements show no evidence of additional impurities in the range of investigation, but suggest that the additional compensation may come from an increased concentration of non-radiative centers.

Temperature Dependent Transport in Microcrystalline PIN Diodes

2000 ◽  
Vol 609 ◽  
Author(s):  
T. Brammer ◽  
H. Stiebig ◽  
A. Lambertz ◽  
W. Reetz ◽  
H. Wagner
Keyword(s):  
Solar Cells ◽  
Fill Factor ◽  
Extraction Efficiency ◽  
Chemical Vapor ◽  
Open Circuit ◽  
Microcrystalline Silicon ◽  
Temperature Dependent ◽  
Dependent Transport ◽  
Silane Concentration ◽  
Interface Effects

ABSTRACTThe optoelectronic behavior of diodes deposited by plasma enhanced chemical vapor deposition was investigated for a series of different silane concentrations in the gas phase. The purpose of this work was to correlate device characteristics with inherent properties of microcrystalline silicon by experiments and numerical simulations. Dark diode characteristics and, therefore, the open circuit voltage behavior of this series were dominated by the bulk properties of the i-layer (equilibrium carrier concentration) as shown by numerical modeling. Measurement of the solar cell output parameters as a function of the temperature showed that the fill factor of solar cells with small silane concentrations is dominated by the dark diode characteristics. This is in contrast to the temperature dependent fill factor of solar cells with large silane concentration which is limited by the extraction efficiency of the photogenerated carriers. Interface effects dominated the temperature dependent blue response. The gain in blue response increased with temperature and silane concentration by up to 200 % which revealed transport limiting material properties in the vicinity of the p/i-interface. This behavior was attributed to the nucleation region.

scholarly journals Excited-State Relaxation in Luminescent Molybdenum(0) Complexes with Isocyanide Chelate Ligands

Inorganics ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 14
Author(s):  
Patrick Herr ◽  
Oliver S. Wenger
Keyword(s):  
Excited State ◽  
Excited States ◽  
Quantum Yields ◽  
Nonradiative Relaxation ◽  
Temperature Dependent ◽  
Tert Butyl ◽  
Thermally Activated ◽  
Ligand Charge Transfer ◽  
Order Of Magnitude ◽  
Electronic Ground

Diisocyanide ligands with a m-terphenyl backbone provide access to Mo0 complexes exhibiting the same type of metal-to-ligand charge transfer (MLCT) luminescence as the well-known class of isoelectronic RuII polypyridines. The luminescence quantum yields and lifetimes of the homoleptic tris(diisocyanide) Mo0 complexes depend strongly on whether methyl- or tert-butyl substituents are placed in α-position to the isocyanide groups. The bulkier tert-butyl substituents lead to a molecular structure in which the three individual diisocyanides ligated to one Mo0 center are interlocked more strongly into one another than the ligands with the sterically less demanding methyl substituents. This rigidification limits the distortion of the complex in the emissive excited-state, causing a decrease of the nonradiative relaxation rate by one order of magnitude. Compared to RuII polypyridines, the molecular distortions in the luminescent 3MLCT state relative to the electronic ground state seem to be smaller in the Mo0 complexes, presumably due to delocalization of the MLCT-excited electron over greater portions of the ligands. Temperature-dependent studies indicate that thermally activated nonradiative relaxation via metal-centered excited states is more significant in these homoleptic Mo0 tris(diisocyanide) complexes than in [Ru(2,2′-bipyridine)3]2+.

Systematic errors in the high-accuracy universal polarimeter: application to determining temperature-dependent optical anisotropy of KDC and KDP crystals

2000 ◽  
Vol 33 (3) ◽  
pp. 938-946 ◽  
Author(s):  
C. Hernández-Rodríguez ◽  
P. Gómez-Garrido ◽  
S. Veintemillas
Keyword(s):  
Optical Anisotropy ◽  
Experimental System ◽  
High Accuracy ◽  
Optical Quality ◽  
Temperature Dependent ◽  
Order Of Magnitude ◽  
Mechanical Elements ◽  
Kdp Crystals ◽  
Detection Unit ◽  
Good Optical Quality

The problem of removing the characteristic parasitic errors of the high-accuracy universal polarimeter method in a linearly birefringent and optically active crystal section is examined. The use of constant parasitic errors typical of each particular polarimetric system is shown to be inappropriate. The parasitics should preferably be determined in each measurement process, since the instrumental parasitics depend not only on the optical and mechanical elements of the experimental system (polarizers, rotators, detection unitetc.), but on sample quality, alignment of the system, and even in many cases on exactly where the light beam passes through the sample. Thus, measurements with different samples give different values of parasitic errors. Such instrumental parasitics can be held within the same order of magnitude for different samples (∼10−4) if they are of good optical quality. However, the parasitics are increased by an order of magnitude (∼10−3) when the samples are of moderate or bad optical quality. Optical anisotropy properties as coefficients of thermal variation of the birefringence of KDC and KDP single crystals and the optical activity of KDP at 632.8 nm wavelength are obtained, in the ranges from room temperature to 353 K and to 373 K, respectively.

Temperature-dependent Hall-effect measurements of p-type multicrystalline compensated solar grade silicon

2012 ◽  
Vol 21 (7) ◽  
pp. 1469-1477 ◽  
Author(s):  
Chiara Modanese ◽  
Maurizio Acciarri ◽  
Simona Binetti ◽  
Anne-Karin Søiland ◽  
Marisa Di Sabatino ◽  
...  
Keyword(s):  
Hall Effect ◽  
Solar Grade Silicon ◽  
Temperature Dependent ◽  
Hall Effect Measurements ◽  
Grade Silicon ◽  
P Type
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