In the context of the monolithic integration of photonics on silicon, the pseudomorphic approach, i.e., growing lattice-matched compounds on Si, is a promising route towards an efficient and long-term stable laser on Si
]. It should overcome the issue of the dramatic number of crystalline defects due to the large lattice mismatch encountered in the growth of most III-V materials onto Si substrates
]. Among binary III-V materials, GaP presents the closest lattice constant to Si (0.37% at 300 K). The perfect lattice matching can even be obtained by introducing 2% of nitrogen in GaP. Recently, the epitaxial growth on Si substrate of GaP and GaPN0.02
has been greatly improved by several groups
]. Various active zones grown on GaP substrate or on GaPN0.02
/GaP/Si have been proposed. The best results have been achieved with compressive strained GaNAsP/GaP quantum wells (QWs) in electrically pumped lasers operating up to 150 K (Si substrate)
] or at room temperature (GaP substrate)
]. However, the electron wave function at the conduction band minimum has a special character
]. It is expected to limit the performances of laser devices yielding high threshold current densities. Indeed, the conduction band of the GaAsP host material has a minimum at the XXY
point on the edge of the Brillouin zone, and partially localized electronic levels related to nitrogen incorporation lie at energies below this minimum. The conduction band minimum of GaNAsP/GaP QWs evidences a predominant localized N character
]. Moreover, the maximum of the emission wavelength reported for such structures with reasonable N content is equal to 980 nm
], which is not yet in the transparency window of Si.
Quantum dot (QD) lasers grown on GaAs or InP substrate display lower threshold currents due to the 0D density of states when compared with QW lasers on the same substrates
]. (In,Ga)P QDs grown on GaP substrate have already been studied, and room temperature electroluminescence has been obtained
]. However, theoretical studies have shown that the electronic band lineups correspond to a borderline case between type I and type II
]. The (In,Ga)As(N)/GaP QDs system has recently attracted much attention. Fukami et al.
] have claimed that the transparency window of silicon may be reached with InGaAsN/GaP QDs when In composition is 50% to approximately 60% and N composition is 1% to approximately 2%. In the following, InGaAs/GaP QDs are studied as a step toward InGaAsN/GaP QDs system. Both room-temperature photoluminescence (PL)
] and electroluminescence
] of InGaAs/GaP QDs have been recently reported. However, the description of the electronic band structure of this QD system is still lacking.
In this paper, we investigate (In,Ga)As/GaP QDs in a low-indium-content range both from the theoretical and experimental points of view. The effects of both indium composition and QD geometry is analyzed through a combination of k·p and tight-binding (TB) simulations. Optical properties are then studied by temperature-dependent photoluminescence and time-resolved photoluminescence (TRPL).