Terahertz Electroluminescence of Shallow Impurities in AlGaN/GaN Heterostructures at Temperatures above 80 K

2018 ◽  
Vol 255 (5) ◽  
pp. 1700421 ◽  
Author(s):  
Ignas Grigelionis ◽  
Vytautas Jakštas ◽  
Vytautas Janonis ◽  
Irmantas Kašalynas ◽  
Pawel Prystawko ◽  
...  
Keyword(s):  
Shallow Impurities

Exciton dynamics in thick GaN MOVPE epilayers deposited on sapphire.

1997 ◽  
Vol 2 ◽  
Author(s):  
J. Allègre ◽  
P. Lefebvre ◽  
J. Camassel ◽  
B. Beaumont ◽  
Pierre Gibart
Keyword(s):  
Layer Thickness ◽  
Buffer Layers ◽  
Rate Equations ◽  
Time Resolved ◽  
Versus Layer ◽  
Level Model ◽  
Shallow Impurities ◽  
Aln Buffer ◽  
Time Resolved Photoluminescence

Time-resolved photoluminescence spectra have been recorded on three GaN epitaxial layers of thickness 2.5 μm, 7 μm and 16 μm, at various temperatures ranging from 8K to 300K. The layers were deposited by MOVPE on (0001) sapphire substrates with standard AlN buffer layers. To achieve good homogeneities, the growth was in-situ monitored by laser reflectometry. All GaN layers showed sharp excitonic peaks in cw PL and three excitonic contributions were seen by reflectivity. The recombination dynamics of excitons depends strongly upon the layer thickness. For the thinnest layer, exponential decays with τ ~ 35 ps have been measured for both XA and XB free excitons. For the thickest layer, the decay becomes biexponential with τ1 ~ 80 ps and τ2 ~ 250 ps. These values are preserved up to room temperature. By solving coupled rate equations in a four-level model, this evolution is interpreted in terms of the reduction of density of both shallow impurities and deep traps, versus layer thickness, roughly following a L−1 law.

Quantum Confinement Effects on the Dielectric Constant of Porous Silicon

1992 ◽  
Vol 283 ◽  
Author(s):  
R. Tsu ◽  
L. Ioriatti ◽  
J. F. Harvey ◽  
H. Shen ◽  
R. A. Lux
Keyword(s):  
Dielectric Constant ◽  
Porous Silicon ◽  
Size Effects ◽  
Quantum Confinement ◽  
Electrochemical Etching ◽  
Index Of Refraction ◽  
Quantum Size Effects ◽  
Quantum Size ◽  
Quantum Confinement Effects ◽  
Shallow Impurities

ABSTRACTThe reduction of the dielectric constant due to quantum confinement is studied both experimentally and theoretically. Angle resolved ellipsometry measurements with Ar- and He-Ne-lasers give values for the index of refraction far below what can be accounted for from porosity alone. A modified Penn model to include quantum size effects has been used to calculate the reduction in the static dielectric constant (ε) with extreme confinement. Since the binding energy of shallow impurities depends inversely on ε2, the drastic decrease in the carrier concentration as a result of the decrease in ε leads to a self-limiting process for the electrochemical etching of porous silicon.

Free and Bound Excitons in GaN Epitaxial Films

1996 ◽  
Vol 449 ◽  
Author(s):  
B.K. Meyer
Keyword(s):  
Thermal Activation ◽  
Chemical Nature ◽  
Epitaxial Films ◽  
Binding Energies ◽  
Temperature Dependent ◽  
Neutral Donor ◽  
Exciton Localization ◽  
Sapphire Substrates ◽  
Shallow Donors ◽  
Shallow Impurities

ABSTRACTWe report on photoluminescence experiments on hexagonal GaN epitaxial films grown on 6H-SiC and sapphire substrates by organo-metallic and hydide vapor phase epitaxy. At low temperatures we observe free and neutral donor bound exciton transitions which allow to establish properties of the free excitons and localisation energies of the bound excitons involving different shallow donors. From temperature dependent luminescence experiments thermal activation energies are determined which measure the exciton localization and donor binding energies. The localization energies of the excitons scale with the respective donor binding energies (Haynes rule). The inter-impurity transitions of neutral donors are observed in fourier transform infra-red absorption. Three shallow donors with binding energies of 34.7 meV, 55 meV and 58 meV can be seen. We present evidence for the chemical nature of the shallow impurities.

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