Comparison of mixed anion, InAsyP1−y and mixed cation, InxAl1−xAs metamorphic buffers grown by molecular beam epitaxy on (100) InP substrates

The structural, morphological, and defect properties of mixed anion, InAsyP1−y and mixed cation, InxAl1−xAs metamorphic step-graded buffers grown on InP substrates are investigated and compared. Two types of buffers were grown to span the identical range of lattice constants and lattice mismatch (∼1...

Ausführliche Beschreibung

Gespeichert in:
Bibliographische Detailangaben
Veröffentlicht in:Journal of applied physics 2004-04, Vol.95 (8), p.3952-3960
Hauptverfasser: Hudait, M. K., Lin, Y., Palmisiano, M. N., Tivarus, C., Pelz, J. P., Ringel, S. A.
Format: Artikel
Sprache:eng
Online-Zugang:Volltext
Tags: Tag hinzufügen
Keine Tags, Fügen Sie den ersten Tag hinzu!
Beschreibung
Zusammenfassung:The structural, morphological, and defect properties of mixed anion, InAsyP1−y and mixed cation, InxAl1−xAs metamorphic step-graded buffers grown on InP substrates are investigated and compared. Two types of buffers were grown to span the identical range of lattice constants and lattice mismatch (∼1.1–1.2%) on (100) InP substrates by solid source molecular beam epitaxy. Symmetric relaxation of ∼90% in the two orthogonal 〈110〉 directions with minimal lattice tilt was observed for the terminal InAs0.4P0.6 and In0.7Al0.3As overlayers of each graded buffer type, indicating nearly equal numbers of α and β dislocations were formed during the relaxation process and that the relaxation is near equilibrium and hence insensitive to asymmetric dislocation kinetics. Atomic force microscopy reveals extremely ordered crosshatch morphology and very low root mean square (rms) roughness of ∼2.2 nm for the InAsP relaxed buffers compared to the InAlAs relaxed buffers (∼7.3 nm) at the same degree of lattice mismatch with respect to the InP substrates. Moreover, phase decomposition is observed for the InAlAs buffers, whereas InAsP buffers displayed ideal, step-graded buffer characteristics. The impact of the structural differences between the two buffer types on metamorphic devices was demonstrated by comparing identical 0.6 eV band gap lattice-mismatched In0.69Ga0.31As thermophotovoltaic (TPV) devices that were grown on these buffers. Clearly superior device performance was achieved on InAsyP1−y buffers, which is attributed primarily to the impact of layer roughness on the carrier recombination rates near the front window/emitter interface of the TPV devices.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.1667006