Photoluminescence lineshape features of carbon δ-doped GaAs heterostructures

Abstract

Photoluminescence lineshape properties of quasi-two-dimensional electron systems in setback δ-doped GaAs heterostructures are studied at liquid helium temperature. Contributions from the ground and the first excited two-dimensional subband are clearly observed. A simple fit to the lineshape including broadening demonstrates that there is an exponential low-energy tail associated with the ground subband. No such tail is observed for the first excited subband. The fit precisely reveals the subband bottom energies, the Fermi energy, the electron temperature and the recombination intensities. A self-consistent calculation of subband properties including the potential contribution of the setback δ-doping reproduces well the subband properties and the recombination intensities.

Influence of recombination center interaction on the photoluminescence of AlGaAs/GaAs heterostructures

“…Simultaneously, there is a redistribution of oscillator strength from the high-to the lowenergy side. With the exception of the lower illuminations the tail exhibits an exponential energy-dependence as was shown previously [5]. The PL line of the first excited subband does not exhibit such a tail and its shape is essentially independent of illumination.…”

“…Consequently one can expect a stronger influence on the space charge density than at 635 nm illumination. Details are discussed in [5,6]. With increasing illumination N S changes from (5.0 ± 0.3) to (4.2 ± 0.3)×10 11 cm −2 for 635 nm and to (2.9 ± 0.3) × 10 11 cm −2 for 532 nm.…”

“…Our n-modulation doped Al 0.35 Ga 0.65 As-GaAs single heterostructures grown on a semi-insulating (1 0 0) GaAs substrate have a standard design [5]. Carbon δ-dopings of N C = 2 and 4 × 10 10 cm −2 setback z C = 24 nm from the interface provide recombination centers in the GaAs buffer.…”

“….). The potential V (z) depends on the electron surface charge densities N S,i in the subbands i, the ionized depletion charges N depl = (N − A − N + D )z depl due to the background doping of the GaAs buffer and the delta-doping charge [5]. The negative charge in the GaAs is balanced by positive charges left to the interface (z < 0), which is held responsible for the observed pinning of the electron Fermi-energy.…”

“…Assuming idealized acceptor properties at sufficient low temperatures, a hat-shape PL line can be expected reflecting the populated part of the constant 2D density of state. However, PL line shapes from intentionally δdoped Al 1−x Ga x As/GaAs heterostructures do reflect the ideal form only approximately [2][3][4][5]. Often a trapezoidal line is observed with a low-energy tail and a reduced intensity on the high-energy side.…”