Tunneling-assisted optical transitions in GaAs delta-doped superlattices

✍ Scribed by V.L. Alperovich; A.S. Jaroshevich; D.I. Lubyshev; V.P. Migal

• Publisher: Elsevier Science
• Year: 1991
• Tongue: English
• Weight: 328 KB
• Volume: 175
• Category: Article
• ISSN: 0921-4526
• DOI: 10.1016/0921-4526(91)90707-l

✦ Synopsis

Optical transitions in delta-doped "sawtooth" n-i-p-i superlattices with various periods are studied experimentally in this paper by photocurrent (PC) and photoreflectance (PR) spectroscopy. The exponential tail of the PC below the band gap eg and oscillations of the PR above eg are due to the Franz-Keldysh effect caused by the homogeneous built-in electric field E in the superlattice. When the period of the superlattices decreases, a monotonic increase of the low-energy wing length and of the above-band gap oscillation period is observed, due to the rise of E. Not only superlanice built-in electric fields but also weaker fields of the buffer layers contribute to the PR spectra. It is shown that different contributions to the PR can be separated experimentally using different lifetimes of the photogenerated electrons and holes. The analogy between the Franz-Keldysh effect in semiconductors and the total reflection of light in optics is discussed.