Oscillator strength of excitons in (In, Ga)As/GaAs quantum wells in the presence of a large electric field

Abstract

The oscillator strength of the fundamental heavy-hole exciton in strained quantum well (QW) InxGa1−xAs/GaAs p–i–n diode heterostructures is calculated by using a variational approach combined with the transfer matrix formalism. Unlike the weak well thickness dependence of the excitonic properties in the absence of electric field, a completely different picture is observed as the strength of the built-in electric field increases. A dramatic reduction of the QW oscillator strength is noticed for thick wells over the entire indium composition range. This is thought to be induced by a very effective quantum confined Stark effect that becomes a limiting factor for maximized absorption properties. In contrast, calculations for highly strained (x>0.20) thin (less than 50 Å) structures evidence oscillator strength values as large as those found with zero electric field. Finally, the results of this study stress adequate well thickness/composition selection for improved performance of optoelectronic multiple QW-based devices such as modulators and photoconverters.

Electro-optical switching between polariton and cavity lasing in an InGaAs quantum well microcavity

“…Such mirrors are inherently easier to grow, are less afflicted to detrimental roughening, hence allowing to obtain large Q-factors much easier than DBRs based on ternary AlGaAs alloys ; c) the substrate is transparent at the emission frequency, which makes transmission studies straight forward, being particularly appealing in resonant studies; d) compared to GaAs QWs, InGaAs QWs allow for a significantly higher flexibility in the design of the QW bandstructure. Consequently, the strain environment (hence the splitting between heavy hole and light holes), the emission wavelength, the oscillator strength and the tuning behavior in electric (via the quantum confined Stark effect) and magnetic fields can be conveniently adjusted via the QW thickness and the composition of the alloy [13][14][15][16]. In fact, it is possible to tune the wavelength band between 830 nm and 1200 nm, which is in particular appealing from the application point of view; e) InGaAs QWs have significantly larger exciton g-factors compared to GaAs/AlGaAs QWs [16], making them very interesting candidates to observe pronounced spinor polariton effects in a magnetic field [17].…”

Minority carrier diffusion lengths and optical self‐absorption coefficient in undoped GaN

“…[19], the increase of L in p-type GaN was attributed to the electron beam induced charging of the doping centers of Mg that yields a significant increase in the minority carrier lifetime. For the AlGaN/GaN or InGaN/GaN structures, this increase is related to the polarization effects [21]. In our case, since the layers are undoped we suspect mainly the observed increase of L to be due to the piezoelectric fields (PEF) caused by the large amount of dislocations (10 8 -10 10 cm -2 ) present in the MOCVD GaN layers.…”

Electron beam-induced current investigation of GaN Schottky diode

“…According to Ref. 18, the increase of L p could be related to the high internal electric field (up to 1 MV/cm) caused by spontaneous and piezoelectric polarization. These effects are now emerging as a dominant factor for the optical and electrical properties of nitride heterostructures.…”