Behaviour of optical transitions in GaAs/AlAs with highly Be δ-doped MQWs

Abstract

We present the photoluminescence properties of highly Be δ-doped GaAs/AlAs multiple quantum wells at liquid nitrogen and room temperatures. Possible mechanisms of carrier recombination focusing on peculiarities of excitonic and free-carriersacceptor photoluminescence are discussed. It is estimated that for Be δ-doped GaAs/AlAs quantum wells (LW = 5 nm) the Mott transition should occur at acceptor concentration NBe some greater than 5 • 10 12 cm −2 .

Low-frequency noise properties of beryllium δ-doped GaAs/AlAs quantum wells near the Mott transition

“…31 Theoretically, from the formula 32 N 1/2 a B % 0.31, where N is the critical 2D doping concentration for the Mott transition and a B is the Bohr radius, the Mott transition for beryllium impurities is at 2.85 Â 10 12 cm À2 ,i fo n e assumes a Be activation energy of 28 meV and the Bohr radius of 2.1 nm. 33 Hence, the doping concentration in sample No. 2 is in the Mott transition region.…”

Radiative Recombination Spectra of Heavily p-Typeδ-Doped GaAs/AlAs MQWs

“…In the high-density limit, the holes are confined to the sheet of ionized impurities and form a 2D hole gas with a 2D subband structure. The critical impurity concentration, N I , for the insulator-metal transition and formation of the subband structure in δ-doped structures can be estimated from the relation: [4,7], where a B is the Bohr radius of the impurity. Based on a simple spherical symmetry model for acceptor species in GaAs/AlAs QWs, and assuming an activation energy E Be = 32 meV, that is a Be = 1.8 nm, the critical concentration is found to be N Be = 2.85 × 10 12 cm −2 .…”

“…In the case of highly δ-doped bulk semiconductors or quantum wells, the impurity-related photoluminescence (PL) spectra suffer drastic changes. Indeed, with increasing the impurity concentrations, the interacting doping species form new states in the valence band, which leads to the creation of a 2D carriers gas and occurrence of the Mott transition [1][2][3][4][5][6][7]. In this article, we report the results of PL experiments carried out on highly Be δ-doped GaAs/AlAs multiple QWs at liquid nitrogen and room temperatures.…”

Differential surface photovoltage spectroscopy of δ‐doped GaAs/AlAs multiple quantum wells below and close to Mott transition

“…It should be noted that the red shift of the PL bands with respect to the DSPV features which is especially pronounced at low temperature (Fig. 2) must be considered when taking into account not only the usual Stokes shift, but also the free electron-acceptor recombination contribution to the PL spectra [11]. We will not examine here the PL spectra in detail.…”

“…For instance, photoluminescence (PL) and photoluminescence excitation (PLE) studies [7,8,[11][12][13] reveal that in centre-doped QWs excitons may survive up to or even above the degenerate limit. The electron density at which the lowest energy excitons are quenched in Si centre-doped QWs is found to be considerably higher (about 10 12 cm -2…”