Charge separation and temperature-induced carrier migration in Ga1−xInxN

Thomas Nuytten

¹

,

Manus Hayne

²

,

Bhavtosh Bansal

³

et al.

Abstract

We have investigated the photoluminescence (PL) of two carefully selected dilute nitride Ga 1−x In x N y As 1−y multiple quantum well structures in magnetic fields up to 50 T as a function of temperature and excitation power. The observation of a nonmonotonic dependence of the PL energy on temperature indicates that localized states dominate the luminescence at low temperature, while magneto-PL experiments give new insights into the nature of the localization. We find that the low-temperature spatial distribution of carriers in the quantum well is different for electrons and holes because they are captured by different disorder-induced complexes that are spatially separated. A study of the thermalization of the carriers toward free states leads to the determination of the free-exciton wave-function extent in these systems and enables an assessment of the localization potentials induced by inhomogeneity in the quantum well.

Heterodimensional charge-carrier confinement in stacked submonolayer InAs in GaAs

“…Thinking more broadly, strong localization of carriers in compositional fluctuations in QWs is also prevalent in nitride systems, both in InGaN/GaN QWs [36] and in dilute nitrides [37]. Indeed, it is widely argued that carrier localization in InGaN/GaN QW devices is crucial to their operation, as it inhibits nonradiative recombination at dislocations [38].…”

Blueshifts of the emission energy in type-II quantum dot and quantum ring nanostructures

“…In solar cells, the type-II QD/QR structure also provides the opportunity for efficient carrier separation and absorption of photons with energy below the band gap of the host semiconductor, improving long-wavelength response. 11,12 Blueshifts of emission energy as a function of increasing excitation power are not routinely seen in type-I systems, but have been observed and attributed to donor-acceptor pair recombination, 13 composition modulation, 14 or state filling. 15 Type-II structures, however, have a characteristically strong blueshift with excitation power, which can affect device operation.…”

Evidence of hot carriers at elevated temperatures in InAs/AlAs0.84Sb0.16quantum wells

“…In a conventional type-I semiconductor excitation power should have negligible effect on the band gap of an intrinsic material. However, in the case of system that suffer spatial separation of carriers either via intentional type-II band gaps [14] or via alloy fluctuations [11] the energy gap can be affected strongly by power, shifting with a P 1/3 dependence for a type-II system, in which increase carrier generation induces a triangular barrier at the interface [14]. In the system investigated here the PL displays a strong low power energy shift, which reduces with increased temperature and at higher power (see Fig 3a).…”

“…This becomes less pronounced at higher power, but still results in a "flattening" of the energy shift at lower temperatures. Such s-shape behavior is indicative of carrier localization and/or alloy fluctuations and has been observed in several systems that suffer materials decomposition and inhomogeneties during sample growth [11][12][13].…”