ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
Photoluminescence and absorption data are presented on AlxGa1−xAs-GaAs superlattices (SLs) disordered into bulk-crystal AlyGa1−yAs (0≤y≤x) by Si or Ge diffusion. The bulk-crystal AlyGa1−yAs produced by impurity-induced disordering (by Al-Ga interchange) is determined by transmission electron microscopy, absorption measurements, and photoluminescence to be homogeneous, with an alloy composition (y) that agrees with the average Al concentration of the SL. For low enough Al concentration (y≈0.23〈yc =0.44, the direct-indirect crossover), in absorption the Ge- or Si-disordered SL exhibits (4.2 and 77 K) the bulk-crystal exciton, which is characteristic of homogeneous alloy (AlyGa1−yAs). Stimulated emission (4.2 and 77 K) in bulk-crystal AlyGa1−yAs is observed ΔE≤50 meV below the band edge via photopumping for both Si- and Ge-disordered SLs of Al concentration yielding y∼0.23 and y∼0.39. Shallow hydrogenlike donor or acceptor states are characteristic of AlxGa1−xAs-GaAs SLs disordered with Ge or with Si. For the Si impurity (i.e., an AlxGa1−xAs-GaAs SL disordered with Si), however, much deeper states (transitions) are observed that saturate at higher photoexcitation levels. These states are attributed to nearest-neighbor or extended Si-Si pairs since similarly disordered AlxGa1−xAs-GaAs SLs doped with Ge do not exhibit deeper states.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.335710
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