Molecular‐beam‐epitaxial growth and characterization of high‐quality alloys and multiple quantum wells on InP substrates using a post‐evaporation‐heated arsenic source
| Autor: | J. L. Bradshaw, R. P. Leavitt |
|---|---|
| Rok vydání: | 1994 |
| Předmět: |
Materials science
Photoluminescence Solid-state physics Condensed matter physics Absorption spectroscopy Superlattice Exciton General Physics and Astronomy Condensed Matter::Mesoscopic Systems and Quantum Hall Effect Molecular physics Condensed Matter::Materials Science Ternary operation Quantum well Molecular beam epitaxy |
| Zdroj: | Journal of Applied Physics. 76:3429-3442 |
| ISSN: | 1089-7550 0021-8979 |
| Popis: | We report the growth of high‐quality As‐based ternary and quaternary alloys lattice matched to InP using a valved arsenic source that can post‐heat the As beam after evaporation. We find that the optimum group‐V‐to‐group‐III beam‐equivalent pressure ratio for growth of (In,Ga)As alloys using this source is considerably lower than values reported previously for growth using conventional As4 sources. Consequently, high‐quality (In,Ga)As, (In,Al)As, and (In,Al,Ga)As alloys (and quantum wells made from these alloys) can be grown under the same growth conditions, i.e., substrate temperatures between about 525 °C and 540 °C and V/III pressure ratios between 10:1 and 15:1. Thick‐film alloys and multiple‐quantum‐well structures grown under these conditions show superior structural and optical quality. Strong excitonic features are observed in the room‐temperature absorption spectra of a number of multiple‐quantum‐well structures with well widths ranging from 30 A to 170 A . Calculations of the exciton transition energies using a simple empirical two‐band model are in excellent agreement with experiment, even for a structure containing quantum wells in tensile strain in which the ordering of ground‐state light‐ and heavy‐hole excitons is reversed. The optical absorption spectrum of a 50‐A ‐period (In,Ga)As/(In,Al)As superlattice shows room‐temperature excitons involving electronic states at both the bottom and top of the minibands. Exciton line widths for these quantum‐well structures, measured using low‐temperature photoluminescence, are consistent with the limits imposed by random alloy fluctuations. We tentatively explain the lower optimum V/III pressure ratio for growth of (In,Ga)As in terms of the increase in kinetic energy of As4 molecules (compared with the kinetic energy of molecules from a conventional As4 source) and the consequent enhancement in the efficiency of dissociation of As4 molecules into As2 molecules at the growing surface. |
| Databáze: | OpenAIRE |
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