Recombination dynamics of type-II excitons in (Ga,In)As/GaAs/Ga(As,Sb) heterostructures

Abstract

Abstract. (Ga,In)As/GaAs/Ga(As,Sb) multi-quantum well heterostructures have been investigated using continuous wave and time-resolved photoluminescence spectroscopy at various temperatures. A complex interplay was observed between the excitonic type-II transitions with electrons in the (Ga,In)As well and holes in the Ga(As,Sb) well and the type-I excitons in the (Ga,In)As and Ga(As,Sb) wells. The type-II luminescence exhibits a strongly non-exponential temporal behavior below a critical temperature of T c = 70 K. The transients were analyzed in the framework of a rate-equation model. It was found that the exciton relaxation and hopping in the localized states of the disordered ternary Ga(As,Sb) are the decisive processes to describe the dynamics of the type-II excitons correctly.

Correlation of optical properties and interface morphology in type-II semiconductor heterostructures

“…The laser excitation energy was above the barrier bandgap energy. Therefore, as discussed in detail in an earlier paper [16,20], besides the type-II PL the spatially direct exciton of the Ga(As,Sb) can be observed at room temperature as well.…”

“…The influence of the thickness of the internal GaAs barrier on the photoluminescence (PL) spectra was studied earlier for both the (Ga,In)As/GaAs/Ga(N,As) and (Ga,In)As/GaAs/ Ga(As,Sb) material systems, respectively [15,16]. For both type-II systems the CT PL increases strongly with decreasing inner barrier thickness in comparison to the emission of the direct excitons.…”

“…Indeed, this transition dominates the spectrum at low temperatures and the Ga(As,Sb) luminescence cannot be observed at 10 K because the electrons tunnel on a timescale faster than the exciton recombination time in Ga(As,Sb). The Ga(As,Sb) emission starts to occur, however, at higher temperatures due to the fact that electrons can occupy higher electronic states by thermal excitation and can return this way to the Ga(As,Sb) QW [16].…”

Band offset in (Ga, In)As/Ga(As, Sb) heterostructures

“…At 100 K the difference of the (Ga,In)As CBO is ≈ −11 % while at 290 K it is ≈ 11 % relative to the CBO at 250 K. It is important to note, that this cannot be realized solely by a respective variation of the valence band offset (VBO) of Ga(As,Sb) without loosing the type-I character of the Ga(As,Sb) peak. It is known from lifetime measurements that the Ga(As,Sb) peak corresponds to a type-I transition at all temperatures 19 . Fig.…”

Dynamical properties and charge accumulation in solar cells with embedded GaSb quantum dots

“…In this system, holes are confined in the GaSb region, whereas electrons are expelled from it. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Much research has been carried out to reveal and clarify the material and device properties including unique electronic states of the GaSb QDs. The spatial separation of electron and hole wavefunctions decreases the recombination of photogenerated carriers, so that a longer carrier lifetime is expected.…”