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Title: Effect of Substrate Surface Defects and Te Dopant Concentration on Crystalline Quality and Electrical Characteristics of AlGaAsSb Epitaxial Layers

Abstract

The influence of GaSb substrate surface defects such as native oxides on the crystalline quality of epitaxial layers was investigated using transmission electron microscopy (TEM). Cross sectional TEM imaging showed that there are discrete defects at the GaSb-substrate/epilayer interface. Secondary ion mass spectroscopy (SIMS) results revealed high oxygen concentration at the interface, indicating that the defects are likely oxides and presumed to be native oxides since other impurities were not detected. High resolution TEM micrographs showed that the subsequent growth of the epilayer continues beyond the defects without any additional defect generation or propagation. Tellurium doped AlGaAsSb epitaxial layers were grown lattice-matched on GaSb substrates and lattice-mismatched on semi-insulating GaAs substrates by organometallic vapor phase epitaxy. Secondary ion mass spectroscopy and Hall data showed that the ratio of carrier concentration to Te concentration decreases significantly when the carrier concentration increases from 2.5 x 10{sup 17} cm{sup -3} to 6.5 x 10{sup 17} cm{sup -3}. TEM imaging showed that the material with heavily doped Te generates a high density (about 10{sup 8} cm{sup 2}) of planar defects (stacking fault) located on (111) planes. Most of the Te-related defects originate at the GaSb buffer layer/AlGaAsSb epilayer interface. In addition, discrete precipitates weremore » observed in the heavily doped AlGaAsSb layer.« less

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Knolls Atomic Power Laboratory (KAPL), Niskayuna, NY
Sponsoring Org.:
USDOE
OSTI Identifier:
875457
Report Number(s):
LM-05K176
TRN: US200605%%22
DOE Contract Number:
DE-AC12-00SN39357
Resource Type:
Conference
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; BUFFERS; DEFECTS; IMPURITIES; MASS SPECTROSCOPY; OXIDES; OXYGEN; RESOLUTION; SUBSTRATES; TELLURIUM; TRANSMISSION ELECTRON MICROSCOPY; VAPOR PHASE EPITAXY

Citation Formats

H Ehsani, N Lewis, G Nichols, L Danielson, M Dashiell, Z Shellenbarger, and C Wang. Effect of Substrate Surface Defects and Te Dopant Concentration on Crystalline Quality and Electrical Characteristics of AlGaAsSb Epitaxial Layers. United States: N. p., 2006. Web.
H Ehsani, N Lewis, G Nichols, L Danielson, M Dashiell, Z Shellenbarger, & C Wang. Effect of Substrate Surface Defects and Te Dopant Concentration on Crystalline Quality and Electrical Characteristics of AlGaAsSb Epitaxial Layers. United States.
H Ehsani, N Lewis, G Nichols, L Danielson, M Dashiell, Z Shellenbarger, and C Wang. Wed . "Effect of Substrate Surface Defects and Te Dopant Concentration on Crystalline Quality and Electrical Characteristics of AlGaAsSb Epitaxial Layers". United States. doi:. https://www.osti.gov/servlets/purl/875457.
@article{osti_875457,
title = {Effect of Substrate Surface Defects and Te Dopant Concentration on Crystalline Quality and Electrical Characteristics of AlGaAsSb Epitaxial Layers},
author = {H Ehsani and N Lewis and G Nichols and L Danielson and M Dashiell and Z Shellenbarger and C Wang},
abstractNote = {The influence of GaSb substrate surface defects such as native oxides on the crystalline quality of epitaxial layers was investigated using transmission electron microscopy (TEM). Cross sectional TEM imaging showed that there are discrete defects at the GaSb-substrate/epilayer interface. Secondary ion mass spectroscopy (SIMS) results revealed high oxygen concentration at the interface, indicating that the defects are likely oxides and presumed to be native oxides since other impurities were not detected. High resolution TEM micrographs showed that the subsequent growth of the epilayer continues beyond the defects without any additional defect generation or propagation. Tellurium doped AlGaAsSb epitaxial layers were grown lattice-matched on GaSb substrates and lattice-mismatched on semi-insulating GaAs substrates by organometallic vapor phase epitaxy. Secondary ion mass spectroscopy and Hall data showed that the ratio of carrier concentration to Te concentration decreases significantly when the carrier concentration increases from 2.5 x 10{sup 17} cm{sup -3} to 6.5 x 10{sup 17} cm{sup -3}. TEM imaging showed that the material with heavily doped Te generates a high density (about 10{sup 8} cm{sup 2}) of planar defects (stacking fault) located on (111) planes. Most of the Te-related defects originate at the GaSb buffer layer/AlGaAsSb epilayer interface. In addition, discrete precipitates were observed in the heavily doped AlGaAsSb layer.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Jan 04 00:00:00 EST 2006},
month = {Wed Jan 04 00:00:00 EST 2006}
}

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  • Tellurium doped AlGaAsSb epitaxial layers were grown lattice-matched on GaSb substrates and lattice-mismatched on semi-insulating GaAs substrates by organometallic vapor phase epitaxy. Secondary ion mass spectroscopy and Hall data showed that the ratio of carrier concentration to Te concentration decreases from 40% to 5% when the Te concentration increases from 4.8 x 10{sup 17} cm{sup -3} to 1.3 x 10{sup 19} cm{sup -3}. Transmission electron microscopy (TEM) showed that the material with heavily doped Te generates a high density (about 10{sup 8} cm{sup 2}) of planar defects. Most of the Te-related defects originate at the GaSb buffer layer/AlGaAsSb epilayer interface.more » In addition, discrete precipitates were observed in the heavily doped AlGaAsSb layer. TEM imaging revealed amorphous defects (likely residual native oxides) along the GaSb substrate/GaSb buffer interface. High resolution TEM imaging revealed high quality growth beyond the GaSb-buffer/GaSb-substrate interfacial defects. The microstructural impact of GaSb-buffer/GaSb-substrate interface defects on the crystalline quality of AlGaAsSb layers is insignificant.« less
  • Heavily Si-doped, strain-relaxed In{sub 0.5}Ga{sub 0.5}As layers are often used as contact layers on N{sup +}GaAs to form nonalloyed ohmic contacts. The present work studies the electrical properties of such In{sub 0.5}Ga{sup 0.5}As layers grown on undoped GaAs buffer layers by molecular beam epitaxy both as-grown and after anneals at temperatures between 300 and 430 {degrees}C. It is found that in the as-grown condition, there is a region of about 150 {Angstrom} extending into the In{sub 0.5}Ga{sub 0.5}As layer contiguous to the In{sub 0.5}Ga{sub 0.5}As/GaAs interface where both the electron concentration and mobility decrease toward the interface. With postgrowth anneal,more » the electron concentration in this region will be further reduced and the width of the region will be increased. The associated activation energy is estimated to be 0.99{plus_minus}0.41 eV. This phenomenon can be fully explained in terms of defect structural changes during anneal. This work provides strong evidence to indicate that the as-grown In{sub 0.5}Ga{sub 0.5}As layers are not in thermodynamic equilibrium and will continue to relax when thermal energy is provided. 15 refs., 7 figs.« less
  • We have grown Nb-doped TiO{sub 2} epitaxial films on (100) and (110)-oriented TiO{sub 2} rutile substrates by molecular beam epitaxy. Nb substitutionally incorporates at cation sites in the rutile lattice, forming Nb{sub {ital x}}Ti{sub 1{minus}{ital x}}O{sub 2} solid solutions. However, the crystal quality and surface roughness of the films depend strongly on the substrate orientation. Surface roughening and defect formation occur at lower values of {ital x} on (100) than on (110). This result is due to anisotropic changes in the metal-oxygen bond lengths within the rutile structure in going from TiO{sub 2} to NbO{sub 2}; there are 1{percent} andmore » 12{percent} changes in the metal atom to octahedron-base oxygen and metal atom to octahedron-vertex oxygen bond lengths, respectively. Every metal atom in the (100) growth surface has in-plane components of the 12{percent} mismatch. However, only half of the metal atoms in the (110) growth plane have such components. Thus, there is substantially larger in-plane lattice mismatch when the growth surface is (100) compared to (110), resulting in surface roughening and formation of defects at a lower doping level for (100)-oriented Nb{sub {ital x}}Ti{sub 1{minus}{ital x}}O{sub 2} epitaxial films. {copyright} {ital 1996 Materials Research Society.}« less
  • Epitaxial single crystal and boron-doped diamond layers were exposed to reactive ion etching in Ar/O{sub 2} plasma (rf power of 25 W and self-bias of 100 V); and the electrical, structural, and electrochemical characteristics of the exposed surface were investigated. Angle-resolved x-ray photoemission spectroscopy (XPS) measurements revealed a nonuniform layer of amorphous carbon at the exposed surface with an average thickness of approximately 4 nm, as confirmed also by atomic force microscopy profiling of selectively etched areas. On highly boron-doped diamond, the plasma-induced damages resulted also in a nonconductive surface layer. This damaged and insulating surface layer remained resistant tomore » graphite-etching chemicals and to rf oxygen plasma but it was removed completely in microwave hydrogen plasma at 700 deg. C. The surface characteristics after the H-plasma process followed by wet chemical oxidation were restored back to the initial state, as confirmed by XPS. Such ''recovery'' treatment had been applied to an all-diamond submicrometer electrode array initially patterned by an Ar/O{sub 2} plasma etching. The electrochemical characteristics of this electrode array were improved by more than two orders of magnitude, approaching theoretical limit for the given geometrical configuration.« less