Radiative Recombination and Carrier Lifetimes in Surface-Free GaAs Homostructures

AbstractWe show that the radiative efficiencies and lifetimes of photoexcited carriers in epitaxial GaAs may be enhanced by 3 to 4 orders-of-magnitude by the preparation of n+, doped layers at surface and substrate interfaces. Samples were prepared by Organo-Metallic Vapor Phase Epitaxy (OMVPE), with n-region thicknesses of 3–10 µm, and narrow layers Si-doped to n+ concentrations of 5×1018 cm-3. Time-resolved luminescence in such structures, under both surface and bulk (near-band-edge) excitation conditions, reveal near-edge-excitonic or band-to-band-dominated recombination spectra, with carrier lifetimes ranging from 1.5 nsec at 1.5 K to nearly 1 µsec at room temperature. This is in contrast to the sub-nanosecond lifetimes typical in conventionally prepared bulk GaAs, but is comparable to the best reported for high-purity LPE-prepared GaAs/AlxGa1-xAs double heterostructures. The spatial distributions of photoexcited carriers in these structures are observed to expand by over an order of magnitude during their 1 µsec room temperature lifetime. The expansion is diffusive, with a measured diffusion constant of 14 cm2/sec at 300 K. This corresponds to a room temperature mobility of 525 cm2/Vsec, comparable to previously measured hole mobilities in bulk p-type GaAs of similar purity. These results are clear evidence that the narrow, heavily doped layers effectively “shield” minority carriers from the interfaces, thereby reducing interface recombination.

Download Full-text

Hydrogenation of Gallium Nitride

MRS Proceedings ◽

10.1557/proc-325-341 ◽

1993 ◽

Vol 325 ◽

Cited By ~ 1

Author(s):

M. S. Brandt ◽

N. M. Johnson ◽

R. J. Molnar ◽

R. Singh ◽

T. D. Moustakas

Keyword(s):

Comparative Study ◽

Conduction Band ◽

Room Temperature ◽

Hole Concentration ◽

Conduction Band Edge ◽

Order Of Magnitude ◽

Si Doped ◽

Donor State ◽

P Type ◽

Mg Doped

AbstractA comparative study of the effects of hydrogen in n-type (unintentionally and Si-doped) as well as p-type (Mg-doped) MBE-grown GaN is presented. Hydrogenation above 500°C reduces the hole concentration at room temperature in the p-type material by one order of magnitude. Three different microscopic effects of hydrogen are suggested: Passivation of deep defects and of Mg-acceptors due to formation of hydrogen-related complexes and the introduction of a hydrogenrelated donor state 100 meV below the conduction band edge.

Download Full-text

Self-Assembled Vanadium Oxide Nanoflakes for p-Type Ammonia Sensors at Room Temperature

Nanomaterials ◽

10.3390/nano9030317 ◽

2019 ◽

Vol 9 (3) ◽

pp. 317 ◽

Cited By ~ 5

Author(s):

Haihong Yin ◽

Changqing Song ◽

Zhiliang Wang ◽

Haibao Shao ◽

Yi Li ◽

...

Keyword(s):

Vanadium Oxide ◽

Room Temperature ◽

Gas Sensing ◽

Electron Microscopies ◽

Ammonia Sensing ◽

Transmission Electron ◽

Order Of Magnitude ◽

Self Assembled ◽

Ammonia Sensors ◽

P Type

VO2(B), VO2(M), and V2O5 are the most famous compounds in the vanadium oxide family. Here, their gas-sensing properties were investigated and compared. VO2(B) nanoflakes were first self-assembled via a hydrothermal method, and then VO2(M) and V2O5 nanoflakes were obtained after a heat-phase transformation in nitrogen and air, respectively. Their microstructures were evaluated using X-ray diffraction and scanning and transmission electron microscopies, respectively. Gas sensing measurements indicated that VO2(M) nanoflakes were gas-insensitive, while both VO2(B) and V2O5 nanoflakes were highly selective to ammonia at room temperature. As ammonia sensors, both VO2(B) and V2O5 nanoflakes showed abnormal p-type sensing characteristics, although vanadium oxides are generally considered as n-type semiconductors. Moreover, V2O5 nanoflakes exhibited superior ammonia sensing performance compared to VO2(B) nanoflakes, with one order of magnitude higher sensitivity, a shorter response time of 14–22 s, and a shorter recovery time of 14–20 s. These characteristics showed the excellent potential of V2O5 nanostructures as ammonia sensors.

Download Full-text

Photoluminescence Characterization of p-type GaN:Mg

MRS Proceedings ◽

10.1557/proc-482-673 ◽

1997 ◽

Vol 482 ◽

Author(s):

Dorina Corlatan ◽

Joachim Krüger ◽

Christian Kisielowski ◽

Ralf Klockenbrink ◽

Yihwan Kim ◽

...

Keyword(s):

Layer Structure ◽

Growth Conditions ◽

Buffer Layers ◽

Near Band Edge ◽

Acceptor Pair ◽

Donor Acceptor ◽

Si Doped ◽

P Type ◽

Mg Doped

AbstractWe report on results of low-temperature photoluminescence measurements performed on GaN films, grown by molecular beam epitaxy (MBE) on sapphire substrates. The GaN films are either Mg doped (p-type) or consist of a Mg-doped layer on top of a Si doped GaN layer (n-type). In the p-doped samples, the sharpness of the donor-acceptor-pair transition is striking, three phonon replicas are clearly resolved. A transition band occurs around 3.4 eV, which becomes dominant for samples with an np-layer structure. The position and the composition of the near band edge transitions are influenced by the growth of the buffer layers. Depending on the growth conditions a transition at 3.51 eV can be observed.

Download Full-text

Impact of Point Defects on the Luminescence Properties of (Al,Ga)N

Materials Science Forum ◽

10.4028/www.scientific.net/msf.590.233 ◽

2008 ◽

Vol 590 ◽

pp. 233-248 ◽

Cited By ~ 14

Author(s):

Shigefusa F. Chichibu ◽

Akira Uedono ◽

Takeyoshi Onuma ◽

Steven P. DenBaars ◽

Umesh K. Mishra ◽

...

Keyword(s):

Point Defects ◽

Emission Band ◽

Room Temperature ◽

Single Point ◽

Luminescent Properties ◽

Shallow Donor ◽

Near Band Edge ◽

Nonradiative Recombination ◽

Time Resolved ◽

Luminescence Efficiency

Threading dislocations (TDs) in (Al,In,Ga)N semiconductors are known to affect the luminescence efficiency of near-band-edge (NBE) emissions in bulk films and quantum structures. However, the principal role of point defects such as vacancies on the luminescent properties has not been fully understood. In this article, impacts of point defects on the luminescence quantum efficiency of NBE emissions and on the intensity of deep emission bands will be described, based on the results of steady-state and time-resolved photoluminescence (TRPL) and positron annihilation measurements. The room temperature nonradiative lifetime (τNR) of the NBE excitonic photoluminescence (PL) peak in polar (0001) and (000-1) , nonpolar (11-20) and (10-10), and zincblende (001) GaN layers prepared by various growth techniques was shown to increase with the decrease in concentration or size of Ga vacancies (VGa) and with the decrease in gross concentration of point defects including complexes, leading to an increase in the NBE PL intensity. As the edge TD density decreased, the concentration or size of VGa tended to decrease and τNR tended to increase. However, there existed remarkable exceptions. The results indicate that the nonradiative recombination process is governed not by single point defects, but by certain defects introduced with the incorporation of VGa, such as VGa-defect complexes. Similar relations were found in AlxGa1-xN alloy films grown by metalorganic vapor phase epitaxy: i. e. τNR at room temperature increased with the decrease in the concentration of cation vacancies (VIII) and with the decrease in gross concentration of point defects. In addition to nonradiative processes, the VIII concentration was found to correlate with the intensity ratio of characteristic deep emission band to the NBE emission (Ideep/INBE). For example, Ideep/INBE at low temperature for the deep emission bands at 4.6, 3.8, and 3.1 eV of AlN epilayers grown by NH3-source molecular beam epitaxy had a linear correlation with the concentration or size of Al vacancies (VAl). Since the relative intensities of 3.1 eV and 3.8 eV bands increased remarkably with lowering the supply ratio of NH3 to Al (V/III ratio) and growth temperature (Tg), they were assigned to originate from VAl-O as well as VAl-shallow donor complexes. The VAl concentration could be decreased by adjusting the V/III ratio and Tg. In the case of AlxGa1-xN alloys, the concentration or size of VIII and Ideep/INBE at 300 K increased simultaneously with the increase in x up to approximately 0.7. Similar to the case for GaN and AlN, the deep emission band was assigned as being due to the emission involving VIII-O complexes.

Download Full-text

Optical Spectroscopy of Ingan Epilayers in the Low Indium Composition Regime

MRS Proceedings ◽

10.1557/proc-595-f99w11.41 ◽

1999 ◽

Vol 595 ◽

Cited By ~ 1

Author(s):

M. H. Crawford ◽

J. Han ◽

M. A. Banas ◽

S. M. Myers ◽

G. A. Petersen ◽

...

Keyword(s):

Room Temperature ◽

Radiative Decay ◽

Thermal Quenching ◽

Localized States ◽

Spectral Variation ◽

Temperature Dependent ◽

Time Resolved ◽

Decay Times ◽

Integrated Intensity ◽

Si Doped

AbstractPhotoluminescence (PL) spectroscopy was carried out on a series of Si-doped bulk InGaN films in the low indium (In) composition regime. Room temperature PL showed a factor of 25 increase in integrated intensity as the In composition was increased from 0 to 0.07. Temperature dependent PL data was fit to an Arrhenius equation to reveal an increasing activation energy for thermal quenching of the PL intensity as the In composition is increased. Time resolved PL measurements revealed that only the sample with highest In ( x=0.07) showed a strong spectral variation in decay time across the T=4K PL resonance, indicative of recombination from localized states at low temperatures. The decay times at room temperature were non-radiatively dominated for all films, and the room temperature (non-radiative) decay times increased with increasing In, from 50-230 psec for x=0-0.07. Our data demonstrate that non-radiative recombination is less effective with increasing In composition.

Download Full-text

Room-temperature photoluminescence lifetime for the near-band-edge emission of (000 1 ¯ ) p-type GaN fabricated by sequential ion-implantation of Mg and H

Applied Physics Letters ◽

10.1063/1.5050967 ◽

2018 ◽

Vol 113 (19) ◽

pp. 191901 ◽

Cited By ~ 15

Author(s):

K. Shima ◽

H. Iguchi ◽

T. Narita ◽

K. Kataoka ◽

K. Kojima ◽

...

Keyword(s):

Ion Implantation ◽

Room Temperature ◽

Band Edge ◽

Near Band Edge Emission ◽

Near Band Edge ◽

Band Edge Emission ◽

Edge Emission ◽

Room Temperature Photoluminescence ◽

Photoluminescence Lifetime ◽

P Type

Download Full-text

Epitaxial Growth and Luminescence Characterization of Si-based Double Heterostructures Light-emitting Diodes with Iron Disilicide Active Region

MRS Proceedings ◽

10.1557/proc-0958-l01-05 ◽

2006 ◽

Vol 958 ◽

Author(s):

Takashi Suemasu ◽

Cheng Li ◽

Tsuyoshi Sunohara ◽

Yuta Ugajin ◽

Ken'ichi Kobayashi ◽

...

Keyword(s):

Decay Time ◽

Room Temperature ◽

Time Resolved ◽

Iron Disilicide ◽

Light Emitting ◽

Si Substrates ◽

Carrier Recombination ◽

Double Heterostructures ◽

Time Resolved Photoluminescence

ABSTRACTWe have epitaxially grown Si/β-FeSi2/Si (SFS) structures with β-FeSi2 particles or β-FeSi2 continuous films on Si substrates by molecular beam epitaxy (MBE), and observed 1.6 μm electroluminescence (EL) at room temperature (RT). The EL intensity increases with increasing the number of β-FeSi2 layers. The origin of the luminescence was discussed using time-resolved photoluminescence (PL) measurements. It was found that the luminescence originated from two sources, one with a short decay time (τ∼10 ns) and the other with a long decay time (τ∼100 ns). The short decay time was due to carrier recombination in β-FeSi2, whereas the long decay time was due probably to a defect-related D1 line in Si.

Download Full-text

The Role of Dopant Concentration on Conductivity and Mobility of CdTe Thin Films

Advances in Condensed Matter Physics ◽

10.1155/2011/910967 ◽

2011 ◽

Vol 2011 ◽

pp. 1-6 ◽

Cited By ~ 10

Author(s):

Ala J. Al-Douri ◽

F. Y. Al-Shakily ◽

Abdalla A. Alnajjar ◽

Maysoon F. A. Alias

Keyword(s):

Thin Films ◽

Room Temperature ◽

Thermal Evaporation ◽

Dopant Concentration ◽

Glass Substrates ◽

Order Of Magnitude ◽

Cdte Thin Films ◽

P Type ◽

Substrate Temperatures

Films of CdTe pure and doped with various atomic percentages of Al and Sb (0.5, 1.5 & 2.5) were prepared, and their electrical properties were investigated. The films were prepared by thermal evaporation on glass substrates at two substrate temperatures (Ts=RT& 423 K). The results showed that the conduction phenomena of all the investigated CdTe thin films on glass substrates are caused by two distinct mechanisms. Room temperature DC conductivity increases by a factor of four for undoped CdTe thin films asTsincreases and by 1-2 orders of magnitude with increasing dopant percentage of Al and Sb. In general, films doped with Sb are more efficient than Al-doped films. The activation energy (Ea2) decreases with increasingTsand dopant percentage for both Al and Sb. Undoped CdTe films deposited at RT are p-type convert to n-type with increasingTsand upon doping with Al at more than 0.5%. The carrier concentration decreases asTsincreases while it increases with increasing dopant percentage. Hall mobility decreases more than three times as Al increases whereas it increases about one order of magnitude with increasing Sb percentage in CdTe thin films deposited at 423 K and RT, respectively.

Download Full-text

Optical Spectroscopy of Ingan Epilayers in the Low Indium Composition Regime

MRS Internet Journal of Nitride Semiconductor Research ◽

10.1557/s1092578300004981 ◽

2000 ◽

Vol 5 (S1) ◽

pp. 717-724

Author(s):

M. H. Crawford ◽

J. Han ◽

M. A. Banas ◽

S. M. Myers ◽

G. A. Petersen ◽

...

Keyword(s):

Room Temperature ◽

Radiative Decay ◽

Thermal Quenching ◽

Localized States ◽

Spectral Variation ◽

Temperature Dependent ◽

Time Resolved ◽

Decay Times ◽

Integrated Intensity ◽

Si Doped

Photoluminescence (PL) spectroscopy was carried out on a series of Si-doped bulk InGaN films in the low indium (In) composition regime. Room temperature PL showed a factor of 25 increase in integrated intensity as the In composition was increased from 0 to 0.07. Temperature dependent PL data was fit to an Arrhenius equation to reveal an increasing activation energy for thermal quenching of the PL intensity as the In composition is increased. Time resolved PL measurements revealed that only the sample with highest In (x=0.07) showed a strong spectral variation in decay time across the T=4K PL resonance, indicative of recombination from localized states at low temperatures. The decay times at room temperature were non-radiatively dominated for all films, and the room temperature (non-radiative) decay times increased with increasing In, from 50-230 psec for x=0-0.07. Our data demonstrate that non-radiative recombination is less effective with increasing In composition.

Download Full-text