Optical recombination from excited states in Ge/Si self-assembled quantum dots

Abstract

We have investigated the photoluminescence of single and multiple layers of Ge/Si self-assembled quantum dots as a function of the excitation power density. We show that the photoluminescence of the quantum dots is strongly dependent on the pump excitation power. The photoluminescence broadens and is blueshifted by as much as 80 meV as the power excitation density increases. Meanwhile, the photoluminescence associated with the two-dimensional wetting layers exhibits only a weak dependence on the pump excitation power. This significant blueshift is interpreted in terms of state filling and recombination from the confined excited hole states in the dots. The photoluminescence data are correlated to the density of states as calculated by solving the three-dimensional Schrödinger equation in these islands with a lateral size of the order of 100 nm.

Narrow photoluminescence peak from Ge(Si) islands embedded between tensile‐strained Si layers

“…5). Similar dependence of the width and position of the PL line from Ge(Si)/sSi islands on pumping power was observed earlier for structures with Ge(Si)/Si(001) islands [21]. Such behavior of the PL signal for Ge(Si) islands is typical for structures with the II-type (indirect in real space) optical transitions [22] and connected with bending of the energy bands due to the coulomb potential of holes accumulated in the islands.…”

Hole confinement and dynamics in δ-doped Ge quantum dots

“…Valence-band filling in Si/Ge dots was studied by Boucaud et al [11]. They concluded that, as a result of the large size and low aspect ratio of the dots in this system, the density of states in the dots differed from the quantum well case only by a factor of 2 (comparing dots with the same height as a given quantum well thickness).…”

Si/SiGe growth by low-energy plasma-enhanced chemical vapor deposition

“…The good germanium crystalline quality has been demonstrated by PL on Ge islands structures [17]. Fig.…”