Characterization of Al0.4Ga0.6As/GaAs aperiodic superlattices by photoluminescence spectroscopy at 2 K
✍ Scribed by S.M. Cao; M. Willander; A.A. Toropov; T.V. Shubina; B.Ya. Mel'tser; S.V. Shaposhnikov; P.S. Kop'ev; J.P. Bergman; P.O. Holtz; B. Monemar
- Publisher
- Elsevier Science
- Year
- 1996
- Tongue
- English
- Weight
- 315 KB
- Volume
- 20
- Category
- Article
- ISSN
- 0749-6036
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✦ Synopsis
We present photoluminescence excitation (PLE) and picosecond time-resolved photoluminescence (TRPL) results of an aperiodic superlattice (ASL) in static electric fields applied perpendicular to the heterojunction interfaces. The ASL consists of nine GaAs quantum wells separated by Al Ga As barriers of varying thickness, such that electronic states in individual QWs are in resonance in a finite electric field (#45 kV cm). We observed a drastic quenching of the photoluminescence intensity when the field is increased over a critical value, and a triple resonance of the heavy-hole exciton states originally confined in neighboring QWs, confirming the formation of an electron quasi-miniband. The TRPL and PLE spectra also suggest that the Coulomb-interaction-induced redistribution of exciton oscillator strength is strongly field-dependent at the resonant field. The ASL structure is demonstrated to achieve control of both optical and transport properties in desired electric fields. Theoretical calculations emphasis on the electron state resonance and the exciton radiative lifetime are performed to understand the experimental data.
1996 Academic Press Limited Heterojunction superlattices (SLs), consisting of periodic quantum wells (QWs) separated by thin potential barriers of a fixed width, have attracted a great interest in recent years [1]. The strong coupling between spatially distributed eigenstates results in unique quantum phenomena such as miniband formation and Wannier-Stark localization. In the presence of an increasing electric field, decoupling of states transforms the miniband into a Stark ladder and eventually leads to twodimensional (2D) subbands [2][3][4][5][6][7]. The regular SLs (RSLs) offer good carrier transport along the growth direction at low fields. But the transport can be significantly reduced at high field due to incoherent relaxation of carriers between subbands. Since the optical transition energies and exciton oscillator strengths (OSs) can be modulated by controlling the interwell coupling strengths, it is possible to design SL structures which allow both spatial electron-hole separation and favorable transport characteristics in an external field. Optical and electrical properties of aperiodic superlattices (ASLs) [8] and irregular superlattices [9] have been investigated under static electric fields. In SM ARTICLE 770 Revise 1st proof 22.7.96